4. Consider a mixing tank with a volume of 50 gallons which isinitially filled with 10 gallons of fresh water. Suppose there isan inflow pipe which pumps in a 1 lb/gallon brine (salt/water)mixture at a rate of 4 gallons per minute, and there is an outflowpipe which removes the mixture from the tank at a rate of 2 gallonsper minute.
(a) Use the given information to derive an initial value problemwhich models the amount of salt in the tank as a function oftime.
(b) Find the solution of the initial value problem.
(c) How much salt in the tank when the tank is full?
