Let Tank A, Tank B, and Tank C be three connected mixing tanks. Figure 1 illustrates a three-tank mixing system such that the directions of flows of liquid in and out of the tanks are indicated by the arrows. Initially, the three tanks contain 140 liters, 80 liters, and 200 liters of pure water, respectively. Suppose 0.4 kg/liter brine runs into the mixing system through Tank A at a rate of 3 liters/min. The well-stirred mixture is exchanged between the three tanks at the indicated rates. The well-stirred mixture drains out of the system from Tank C at a rate of 3 liters/min. a) Calculate the volume of liquid in each tank at time t. b) Construct a system of linear differential equations representing the mathematical model for the above-mentioned mixture problem. (Do not solve the model)