(1 point) A tank, containing 1620 liters of liquid, has a brine solution entering at a constant rate of 2 liters per minute. The well- stirred solution leaves the tank at the same rate. The concentration within the tank is monitored and found to be - 900 c(t) = kg/L. 90 a. Determine the amount of salt initially present within the tank. Initial amount of salt = 18 kg b. Determine the inflow concentration cin (t), where Cin(t) denotes the concentration of salt in the brine solution flowing into the tank. Cin(t)=-18/90e^(-t/900) kg/L