(a)A firm manufacturers two products. Each product must be processed through two departments. Product A requires 2 hours per unit in department 1 and 4 hours per unit in department 2. Product B requires 3 hours per unit in department 1 and 2 hours per unit in department 2. Department 1 and 2 have, respectively 60 and 80 hours available each week. Profit margins for the two products are, respectively Sh.3 and Sh.4 per unit. Using graphical method, determine the number of units that should be produced in order to maximize profit.