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?

Jason is looking for an engagement ring to offer his girlfriend. he has found a similar ring at each of four different jewelry stores. he doesn't have enough money to pay for the ring in cash, so he is planning on opening a line of credit (credit card) at the store he ends up buying the ring from. the chart below outlines the difference in the price of the rings the different stores offer as well as the difference in credit options. jason plans to pay off the ring purchase in 36 months. according to the information in the table, which of the jewelry stores will have the cheapest ring in the end?