4. OPC Plc makes product X. a. Complete the following purchase budget of OPC Plc. (10 marks) March Quarter January 55,000 units February 50,000 units Required production 78 78 78 Direct materials needed to make one unit of product X 980,000 g Total materials needed for production Desired closing inventory is three and half percent (3.5%) of next month's production needs 20,000 g Planned opening inventory 1,350 g Total material purchase needs (8) Total purchase cost () 1,212, 137.50 b. In no more than 200 words, discuss the usefulness of incremental budgeting and zero-based budgeting. (10 marks]