S&J Ltd make 4 products W,X,Y and Z. All 4 products are produced using the same machinery and for March 2023 the company is contracted to supply 5000 units of each product. Only 40000 machine hours will be available in March but any unmade production can be bought in from a subcontractor. 1 unit of W 1 unit of X 1 unit of Y 1 unit of Z Machine Hours p.u. Variable Cost p.u. Bought in price p.u. 1 3 4 24 36 48 56 40 50 60 70 (a) How many of each product should be manufactured by the company and how many should be bought from the subcontractor to minimise costs in March?