Generalize the model given in equation (8) on page 24 by assuming that the large tank initially contains N₀ number of gallons of brine, r_in and r_out are the input and output rates of the brine, respectively (measured in gallons per minute), c_in is the concentration of the salt in the inflo , c(t) the concentration of the salt in the tank as well as in the outflow at time t (measured in pounds of salt per gallon), and A(t) is the amount of salt in the tank at time t > 0.