A manufacturer uses large quantities of a purchased part in his assembly operations. The following data are relevant to the problem of determining the optimal lot size of the purchased part: - Annual requirements: 50,000 units over the year. - Cost of giving one order: $7,500. - Annual cost of interest: 20 percent of the purchasing cost. - Supplier's price schedule: a purchasing charge of per unit determined according to the following schedule: Find the optimal lot size and the minimum total annual average cost if: a) the supplier implements all-units discount policy. b) the supplier implements incremental discount policy