Operator

Ladies and gentlemen, please remain on the line. Your conference will resume shortly.
Presenters, please continue.

Tongbo Liu

Okay. Additionally, our enrollment surged by 22.8% to a historical high of over 175,000, demonstrating the enhanced proficiency in acquiring students. This improvement reflects our dedicated initiatives to attract new users and enhance user retention and engagement by refining our cost offerings to meet diverse lending needs.
Looking ahead, we remain optimistic about our long-term profitability. We endeavor to closely monitor and enhance student experience across all phases of teaching, learning (technical difficulty). Moving forward, we are dedicated to delivering exceptional services and products, while exploring avenues for further business growth and operational efficiency improvement.
Now let's turn to the performance of each of our major course programs. Our post-secondary programs now account for 14.3% of our total revenue, a testament to our strategic structural optimizations and alignment with our latest investment return goals. Given the structural makeup of educational attainment with the Chinese population, the universal access to compulsory education and the prevailing demands of the job market, we are still convinced these programs are in demand, and we remain dedicated to providing premium courses to our in-progress students.
In addition, we'll continue to pursue B2B (inaudible) decisively, leveraging our deep-rooted expertise in this area. Through our self-planned (inaudible) we provide small- and medium-sized organizations with comprehensive solutions, including extensive course content, authentic examination questions, and advanced teaching management tools to help them improve their teaching and content distribution abilities.
Our aim is to provide our partners with advanced, intuitive tools that can significantly improve the learning experience for their users and ultimately enhance the quality and efficiency across the industry. The sector, including professional certifications, professional skills, and [interest] programs continue to be our primary growth engine, contributing 74.4% to the total revenue. Interest program, in particular, exhibited a 22.2% year-over-year growth.
In this sector, our strategy remains unwavering to continuously expand our course offerings, attract a broader audience through curriculum, enhanced customer rate -- retention rates, and ultimately optimize the lifetime value of our users. This approach has proven successful as evidenced by a [32.4%] increase in new enrollments in our interest-based education program this quarter, underscoring the effectiveness of our strategic initiatives.
Through ongoing practice, we have gained fresh insight into different age groups, shifting our approach to course design and service (technical difficulty) for example, unlike younger individuals whose educational pursuits are often career-oriented or driven by external expectations, more mature learners seek learning experiences that enrich their lives, bring joy, and foster meaningful connection. The fundamental difference necessitates a substantial departure from traditional education and paradigms in both curriculum development and service delivery models.
Simply migrating existing course online does not suffice. Instead, we master intricately aligned with the unique needs of this demographic to enhance and customize our offerings accordingly. Moreover, the service delivery models should be adaptable and considerate of their physical and cognitive abilities, emphasizing the creation of a supportive and inclusive learning environment that encourages active participations and continuous engagement.
We have consistently pushed the boundaries of our innovative curriculum and achieved multiple milestones through industry integration. A prime example is our educational travel adventure projects, launched in March 2023, which are well suited for the elderly. At the end of the first quarter of 2024, we have already crossed over 14 -- 40 study (inaudible) [rules].
According to McKinsey's 2024 China Consumer Trends Report, senior citizens in first-tier cities have -- spending expectations for travel that notably exceed those who -- of the general population, marking this as a burgeoning market segment. These consumers are not primarily driven by price when deciding which travel products to purchase. Instead, they seek diverse, high-quality, and unique travel experiences, making premium travel products, particularly well-received.
Setting ourselves apart from traditional tourist offerings, we seamlessly integrate components from our courses, such as the art of traditional Chinese [cuisine] of the journey, enriching that experience with culture, depth, and immersive learning opportunities. In the first three months of (inaudible) alone, revenue from international travel adventure projects has already surpassed the [35%] of the earnings for the entire of 2023. In the future, we will expand our efforts into other areas of our elderly users, a wider array of products and into a ton -- aiming to extend the customer life cycle.
Furthermore, as a company in embracing cutting age artificial intelligence technology, we have steadily enhanced our integration of AI into our business operations. For example, we streamlined content creation processes focused on increasing page views and refined multiple models to deliver personalized teaching. This led to a reduction in production time and significant boosted the efficiency of our operational team.
We will continue to monitor updates in large models and apply to our [business], ultimately enhancing our users' learning experience. While we have achieved significant milestones, it's essential to acknowledge that we also faced challenges. Moving forward, we are dedicated to adjusting our strategies to navigate market [uncertainties]. Our focus will remain on delivering high-quality education, expanding our market presence, and prioritizing shareholder value.
Thank you for your presence today. With that, I will turn the call to our Financial Director Hangyu to run through our financials.

Hangyu Li

Thank you, Tongbo. Hello, everyone. I'd like to introduce our (technical difficulty) total results. All figures are denominated in RMB, unless explicitly specified otherwise.
For the quarter, we have achieved net income of RMB112.7 million with net income margin of 21.5%. Our tenth consecutive quarterly net income margin above 20%. The stable margins in recent quarter are due to our continued efforts to improve operational efficiencies and optimize our cost structure. Also, our revenue declined year over year due to changes in our product mix. The successful strategy of balanced, sustainable growth, and profitability brought our cash operating inflows of RMB76.4 million in the quarter.
At the end of the first quarter, the total balance of cash, cash equivalents, restricted cash, and short-term investments totaled RMB983.2 million, an increase of 8.2% from the end of the previous year. Our healthy financial condition gives us the confidence to face the challenges ahead. This will enable us to capitalize on emerging opportunities, strengthening our leadership position in the industry and continue to create value for our shareholders.
Now let me walk you through some of our key financial results for the first quarter of 2024. All comparisons are year over year unless otherwise noted. In the first quarter of 2024, net revenues decreased by 7.7% to RMB523.2 million from RMB566.9 million in the first quarter of 2023. The decrease was primarily driven by the decline in gross billings from post-secondary courses over the recent quarters, partially offset by the growth in revenues from sales of goods such as books and learning materials.
Cost of revenues increased by 13.2% to RMB77.2 million in the first quarter of 2024 from RMB68.2 million in the first quarter of 2023. The increase was primarily due to the growth in the cost of revenues from sales of goods.
Gross profit decreased by 10.6% to RMB446.1 million in the first quarter of 2024 from RMB498.7 million in the first quarter of 2023. In the first quarter of 2024, operating expenses was RMB341.1 million, representing a 6.4% increase from RMB320.7 million in the first quarter of 2023.
Sales and marketing expenses increased by 11.1% to RMB301.6 million in the first quarter of 2024 from RMB271.4 million in the first quarter of 2023. The increase was mainly due to the growth in spending on sales activities, including enhanced compensation for sales personnel as well as increased spending on branding and marketing activities focusing on interest courses offering.
General and administrative expenses decreased by 17.9% to RMB32.6 million in the first quarter of 2024 from RMB39.6 million in the first quarter of 2023. The decrease was mainly due to the decline in rental expenses as certain leases for office space were partially terminated in 2023 before expiration of the lease term for cost savings.
Product development expenses decreased by 27.6% to RMB7 million in the first quarter of 2024 from RMB9.7 million in the first quarter of 2023. The decrease was mainly due to decline in compensation expenses related to headcount reduction of our product development personnel. Net income for the fourth quarter of 2024 was RMB112.7 million as compared to RMB180.1 million in the first quarter of 2023. Basic and diluted net income per share was RMB16.44 in the first quarter of 2024.
As of March 31, 2024, the company had RMB803.5 million of cash, cash equivalent, and restricted cash; and RMB179.7 million of short-term investments as compared to RMB766.4 million of cash, cash equivalents, and restricted cash; and RMB142.1 million of short-term investments as of December 31, 2023.
As of March 31, 2024, the company had a deferred revenue balance of RMB1,044.9 million as compared to RMB1,113.9 million as of December 31, 2023.
Regarding the outlook for the second quarter, we had net revenues to be between RMB480 million and RMB500 million, a year-over-year decrease of 5% to 8.8%. This outlook is based on the current market conditions and reflects the company's management's current and preliminary estimates of market operating conditions and customer demand, which are all subject to change.
With that, I'd like to open up the call to the questions. Operator?

Question and Answer Session

Operator

(Operator instructions)
At this time, we're showing no further questions, so this will conclude our question-and-answer session. I'd now like to turn the conference back to Yuhua for any closing remarks.

Yuhua Ye

Once again, thank you, everyone, for joining today's call. We look forward to speaking with you again soon. Good day and good night.

Operator

Thank you. This concludes today's conference call. Thank you for participating. You may now disconnect.