Well, after working the problem I came up with 50625 ft-lb. Wrong. Ugh.

I tried using a linear relationship. y=12/5y+12

dV=9(12/5y+12) dy

dV=108/5*y + 108

I multiplied by the density of water(62.5 lb/ft^3). d=m/v then d*v=m.

dV=1350y+6750 dy

Now I integrate from zero to five.

[675x^2+6750x](zero to five)=50625 ft-lb...