A dealer wishes to purchase a number of fans and sewing machines. He has only Rs. 5760 to invest and has space for at most 20 items. A fan costs him Rs. 360 and a sewing a machine Rs. 240. His expectation is that he can sell a fan at a profit Rs. 22 and a sewing machine at a profit of Rs. 18 . Assuming that he can sell all the items that he can buy,how should he invest his money in order to maximise the profit? Formulate this as a linear programming problem and solve graphically.