A tank initially holds 80 gal of a brine solution containing 8/1 lb of salt per gallon. At t = 0, another brine solution containing 1 lb of salt per gallon is poured into the tank at the rate of 4...

A tank initially holds 80 gal of a brine solution containing
8/1 lb of salt per gallon. At t = 0, another brine solution containing 1 lb of salt per gallon is poured into the tank at the rate of 4 gal/min while the well-stirred mixture leaves the tank at the rate of 8 gal/min.
a. Find the amount of salt in the tank at any time t.
b. Determine when the tank will be empty.
c. Determine when the tank will hold 40 gal of solution.
d. Find the amount of salt in the tank when the tank contains exactly 40
gal of solution.
e. Determine when the tank will contain the most salt