I don't understand the question either. The only answer I can think of is possible that the volume would be entered in the unit cubed. By that I mean: 4 in.^3 while surface area I think would just be in.^2 (squared). I'm not 100% sure that is what they are asking but if it is this should be the answer. Hope it helps.
Answer:
3.75+7.5 = 11.25
20 dollars in total how much change.
20 - 11.25 = 8.75
$8.75 change
Simply take 6 percent from 1800 to find the commision earned.
1800x6% is 108.