Subscribers to my recommendation service get access to recommendations about local workers, such as doctors, plumbers, and so on. I believe the number of new subscribers I obtain each month depends on price, as follows:

Assume each subscriber remains a subscriber for one year. In addition to subscription fees, I make money when a subscriber clicks an ad. The average subscriber views 10 ads per year. What price will maximize my total revenue?

Price $10 $20 $30 Demand 20,000 15,000 6,000