$6.$ Refer to number $5$ above. The journal entry to be recorded when twelve of the units were actually replaced during the month would include:

a$.$ a credit to Cash for $$1,200$

b$.$ a debit to Warranty Expense for $$1,500$

c$.$ a debit to Estimated Product Warranty Liability for $$1,200$

d$.$ a credit to Inventory for $$1,500$