4. ABC company uses transistors every month. For each transistor, cach order cost is SA and the annual holding cost is 15 per cent of unit cost. The unit cost depends on the quantity ordered as follows: Quantity Unit Cost (5) 1-99 10 100-299 9.6 300-599 9 600+ >> Assume that demand has a constant rate and do not stockout: if A=66 c=5 C a) What is the optimal order size? (15p) b) Determine the yearly order quantity (Sp) c) Determine the time between two orders. (5p)