Whitmer Inc. sells to customers all over the U$.$S$.,$ and all receipts come in to its headquarters in New York City. The firm's average accounts receivable balance is $$2\mathrm{.}5$ million, and they are financed by a bank loan at an $6\mathrm{.}75\%$ annual interest rate. The firm is considering setting up a regional lockbox system to speed up collections, and it believes this would reduce receivables by $20\%.$ If the annual cost of the system is $$15,000,$ what pre$-$tax net annual savings would be realized?

a$.$ $$18,750$

b$.$ $$20,438$

c$.$ $$16,313$

d$.$ $$21,375$

e$.$ $$22,313$