A tank contains 50 litres of pure water. At time t = 0, saltwater of concentration 2 kilograms of salt per litre is poured into the tank at a rate of 10 litres per minute, mixed thoroughly, and then drained at a rate of 10 litres per minutes. Let S be the amount of salt in the tank in kilograms at time t minutes. (a) Show that (L3 (b) State the value of E when t = 0. (c) Solve the differential equation to determine S in terms of t. (cl) State the value S approaches as t a 00