A water reservoir has the shape of a right circular cone with its circular base of radius 100 m at ground level (m). rain fills the reservoir over the winter; when full, the reservoir depth is 80 m. in summer, water from the reservoir is pumped up to ground level for drinking, irrigation, etc. at the end of the summer, the volume of water left in the reservoir is only 1/4 of its full capacity.

(a) find the depth of the water in the reservoir at the end of the summer.

(b)find the total work done to lift water out of the reservoir during the summer.