= 2. A 50-gal tankinitially contains 10 gal of fresh water. At t = 0, a 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 2 gal/min. Find: a) the amount of time required for overflow to occur b) the amount of salt in the tank at the moment of overflow. [10 marks]