Suppose that at $370$ K pure solid A is in equilibrium with a liquid solution containing $60$ mol$\%$ A and $40$ mol $\%$ B$.$ Use this information and the Margules equation, estimate the composition of the A and B liquid mixture when it is in equilibrium with pure solid B at the same temperature. The melting point temperature and the heat of fusion of solid A and B are: A $400$K and $-3000$ cal$/$mol $,$ B $390$K and $-2800$ cal$/$mol$.(1$cal$=4\mathrm{.}184$J$)$