A A gallon reservoir near the coast was built before the des

A A gallon reservoir near the coast was built before the desalination water treatment plant and distribution piping to the city were complete. The plant was capable of producing water with zero salt concentration, but would blend the water later with sea water to yield~150 mg/L. However, this is not your concern for this problem. To ensure that the new concrete walls of the reservoir would not be exposed to direct sunlight for extended periods, it was filled with sea water (salt concentration B mg/L). Once the treatment plant started operating, the plant manager had to reduce the salt concentration to Cmg/L before the water could be delivered to the customers. She can do it in one 2. of two ways: She can start flushing it out by keeping the tank well mixed while running in a hose with desalinated water at a flowrate of D gallons per minute, and keeping the volume in the tank a. constant. She can empty out some of the contaminated water and fill the tank up again with enough clean water to get minute, and the maximum flow of clean water is D gallons per minute as above b. Cmg/L. The maximum rate at which the tank will empty is E gallons per If she intends to do this job in the shortest time possible, which alternative will she choose? Note: 1 gallon- 3.785 liters (clearly, these two numbers have the same precision) A= 7,5892, B-38, 105.5, C= 1.3163, D= 663, E-104.5

Solution

She would prefer the second method because in second method volume can be kept constant and water can be desalinated