One of the problems with Africa's rainfall is: Group of answer choices its variability from year to year in some of the marginal zones at the equator there is not enough rainfall to support agriculture that it only rains in the winter the large amount of rainfall in Namibia

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?