when manufacturing overhead has a credit balance, overhead is overapplied. Overapplied overhead means that the overhead assigned to work in process is greater than the overhead incurred. Also, since the amount is immaterial, it should be closed in cost of goods sold.
The adjusting entry for the overapplied over-head is:
b. debit factory overhead $5,600; credit cost of goods sold $5,600.
After posting this entry the factory overhead account will have a zero balance.
Hope it helps!