A tank initially holds 100 gallons of a brine solution containing - 1b of salt per gallon. At t = 0, another brine solution containing 2 lbs of salt per gallon is poured into the tank at the rate of 5 gal/min, while the well-stirred mixtures leave the tank at the rate of 10 gal/min. Find: a) The amount of salt in each tank at any time t. b) The amount of salt in the tank when the tank contains exactly 50 gal of brine