what is the total of your discretionary expenses?
expense amount
mortgage $1,034.78
utility bill $168.34
credit card $54.21
groceries $98.75
khakis (not required for work) $45.88
$144.63
$45.88
$100.09
$198.84

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?