A tank contains 90 kg of salt and 2000 L of water. A solution of a concentration 0.0225 kg of salt per liter enters a tank at the rate 5 L/min. The solution is mixed and drains from the tank at the same rate. (a) What is the concentration of our solution in the tank initially? concentration = (kg/L) (b) Find the equation for the amount of salt in the tank after t hours. amount(t) = (kg) (c) Find the amount of salt in the tank after 5 hours. amount = (kg) (d) Find the concentration of salt in the solution in the tank as time approaches infinity. concentration = (kg/L)