10. (10) A supermarket withdraws an average of $15,000 in cash per month from it Treasury Bond account to replenish its idle cash. The current yield on the bonds is 8 percent per year. The brokerage transaction fee per order is $18. a. What is the optimal amount for each withdrawal? b. How often should these optimal withdrawals be made? c. What will be the annual total cost of both ordering and carrying costs with the optimal policy