The surface area is 72 ft.^2.
The number in the parentheses is the rate of change. Because this number is less than 1 it is a decrease, so it is a decay.
The percent decrease is 1 - 0.63 = 0.37 = 37% decrease
1 meter = 100 centimeters, so 120 centimeters equal to 1.2 meters.
The question is "What's Stella's opportunity cost of working on her serve for an hour?" The rest of the info looks like it's meant to confuse you. They charge $10 an hour. She values an hour of her time at $20. I believe that means she would pay $20. Hope this helps!
