Classify the following adjusting entries as involving prepaid expenses (PE), unearned revenues (UR), accrued expenses (AE), or accrued revenues (AR).

a. To record expiration of prepaid insurance. ^

b. To record revenue earned but not yet billed (nor recorded).

c. To record wages expense incurred but not yet paid (nor recorded).

d. To record annual depreciation expense.

e. To record revenue earned that was previously received as cash in advance.