McLarry manufacturing firm paid $12,000 for a repair on one of its machines. After this repair, the productivity of this machine increases from producing 100 units per hour to 120 units per hour. The journal entry to record this repair will include:

a. a credit of accumulated depreciation account $12,000.

b. a debit of repair expense $12,000.

c. a debit of maintenance expense $12,000.

d. a debit of machine account $12,000.