I think a is the best answer.
I think it might be 43.3in^2
63/9=7
21/7=3
answer is 9/3
Only 27.5% of the people asked would pay the $100 [(11/40)*100]. You need 38 out of 40 people to say they would pay $100 for a 95% confidence. I got 38 from trial and error. Hope this helps.