The president of the world bank has asked you to calculate the average population growth rate of hungary from 1970 to 2010. you know the population was about 10.4 million in 1970 and about 9.5 million in 2010. the average growth rate is about percent.

Atennis club charges a monthly membership fee of $150 and charges it members $10 per hour to use a court. there's also $500 fee to become a member. stella joined the tennis club last spring, and she has been a member for 5 months. she has been playing 10 hours of tennis each month. stella values an hour of her time at $20. during a boring afternoon meeting, stella thinks about reserving a court to work on her serve for an hour tonight. what's stella's opportunity cost of working on her serve for an hour?