)a 200 gallon tank initially contains 50 gallons in which are dissolved 5 pounds of salt. the tank is flushed by pumping pure water into the tank at a rate of 3 gallons per minute and a well-mixed solution is pumped out at a rate of 2 gallons per minute. compute the time when the tank has filled, then write the initial value problems which describes amount of salt in the tank at any time before the tank is full. you need not solve the equation.