The bottom radius of the reservoir is: 4/2 = 2m.

Water pumping per second: 3. 14× 4× 10 = 502.4 cubic centimeters.

Reservoir volume: 3. 14× 2× 2.5 = 3 1.4 cubic meters = 31400,000 cubic centimeters.

It takes time to pump water out of the reservoir: 3 1400000÷502.4=62500 seconds =