Differential equations:
salt water pours into a full 20 litre tank at a rate of 2 l/min . the inflow initial concentration is 2 kg/l but after 30 minutes the inflow concentration switches to 1 kg/l . the brine in the tank is well mixed and it drains out at a rate of 2 l/min . call y the grams of salt in the tank at time t. the tank is initially full of fresh water. solve the differential equation that models the salt in the tank.
bonus: what is the maximum kg of salt ever in the tank?