Baker's Confectionery just received a check from a customer for $$1,289$ that it has recorded in its checkbook but has not yet deposited this check into the bank. After recording this check, the firm has a bank balance of $$16,218$ and a book balance of $$16,309.$ All the firm's other deposits have cleared and those funds are currently available.

a$)$ Determine the book balance prior to last deposit

b$)$ Calculate the amount of the disbursement float