Suppose that we have two tanks(X and Y) between which a mixture of brine flows. Tank X contains 400 litres of water in which 200 kilograms of salt has been dissolved and tank Y contains 400 litres of pure water. Fresh water is pumped into tank X at the rate of 700 litre per hour and brine is pumped into tank Y from tank X at the rate of 700 litre per hour. Brine is also drained at a rate 700 litre of brine per hour from tank Y. All brine mixture are well stirred. Find the amount of salt (in KG) in X and Y at any time t.