Hi Yoonji,

This is Mr. Rhee.  Thank you for telling me that you enjoyed my AP Calculus lectures. I hope you learned alot.

I looked at your attached solution and found one mistake from converting ft^3 to in^3.

1 foot= 12 in (inches).

1 ft^3=1 ft X 1 ft X 1 ft = 12 in X 12 in X 12 in = 1728 in^3 (not 144 in^2)

Hope you resolve your problem.

Best regards,

Mr. Rhee