Identify caching opportunities

You're optimizing a product catalog API that serves an e-commerce website. The API handles several types of requests: product details (accessed 1000x/day per product, product data changes 2x/week), real-time inventory counts (accessed 500x/day per product, inventory changes 50x/day), user session data (accessed 100x/session, expires after 30 minutes), and daily sales reports (accessed 5x/day, generated once daily at midnight).

Which data type would benefit MOST from caching?