Consider the two tanks shown in the figure below. Assume that tank A contains 50 gallons of water in which 25 pounds of salt is dissolved. Suppose tank B contains 50 gallons of pure wates Liquid is pumped into and out of the tanks as indicated in the figure; the mixture exchanged between the two tanks and the liquid pumped out of tank B are assumed to be well stirred. We wish to construct a mathematical model that describes the number of pounds x1(t) and x2(e) of salt in tanks A and B, respectively, at time t. pure water 3 gal/min mixture 1 gal/min mixture 4 gal/min This system is described by the system of equations Exp 1 + dt dx2 2 - x1 - dt 50 2 mixture 3 gal/min with initial conditions x1(0) 25, x2(0) 0 (see (3) and the surrounding discussion on mixtures on page 107). What is the system of differential equations if, instead of pure water, a brine solution containing 2 pounds of salt per gallon is pumped into tank A? dxy dt dx2 dt