Water at 25°C is pumped at constant rate of 7.56 m3/h from a large reservoir resting on the floor to the open top of an experimental absorption tower. The point of discharge is 8 m above the floor, and frictional losses in a 2-in sch. 80 pipe from the reservoir to the tower amount of 0.05 BTU/lbm. At what height in the reservoir must the water level be kept if the pump can develop only 250 W?