Solve Exercise 22 if the brine solution is introduced at the rate of 1 gal per minute while the rate of outflow stays the same.

Exercise 22

A tank holds 100 gal of water that contains 20 lb of dissolved salt. A brine (salt) solution is flowing into the tank at the rate of 2 gal per minute while the solution flows out of the tank at the same rate. The brine solution entering the tank has a salt concentration of 2 lb per gal.
(a) Find an expression for the amount of salt in the tank at any time.
(b) How much salt is present after 1 hour?
(c) As time increases, what happens to the salt concentration?