Atank contains 90 kg of salt and 2000 l of water. water containing 0.4kgl of salt enters the tank at the rate 6 lmin. the solution is mixed and drains from the tank at the rate 3 lmin. a(t) is the amount of salt in the tank at time t measured in kilograms.(a) a(0) =equation editorequation editor(kg)(b) a differential equation for the amount of salt in the tank isequation editorequation editor=0. (use t, a, a', a'', for your variables, not a(t), and move everything to the left hand ) the integrating factor isequation editorequation editor(d) a(t) =equation editorequation editor(kg)(e) find the concentration of salt in the solution in the tank as time approaches infinity. (assume your tank is large enough to hold all the solution.)concentration =equation editorequation editorkgl