A tank contains 70 kg of salt and 2000 L of water. Watercontaining 0.4kg/L of salt enters the tank at the rate 16L/min. Thesolution is mixed and drains from the tank at the rate 4L/min. A(t)is the amount of salt in the tank at time t measured inkilograms.
(a) A(0) =Â Â (kg)
(b) A differential equation for the amount of salt in the tankis  =0=0. (Use t,A, A', A'', for your variables, notA(t), and move everything to the left hand side.)
(c) The integrating factor is
(d) A(t) =Â Â (kg)
(e) Find the concentration of salt in the solution in the tank astime approaches infinity. (Assume your tank is large enough to holdall the solution.)
concentration =Â Â kgL
