7. (8 pts) Choose either (a) or (b). You only need to solve one problem. (a) A water tank is shaped like an inverted cone with height 8 m and base radius 1 m. If the tank is full, how much work is required to pump the water to the level of the top of the tank and out of the tank? Use 1000 kg / m for the density of water and 9.8 m/s for the acceleration due to gravity. (b) A trough is filled with a liquid of density 875 kg/m. The ends of the trough are equilateral triangles with sides 10 m long and vertex at the bottom. Find the hydrostatic force on one end of the trough. (Use 9.8 m/s for the acceleration due to gravity.)