An examination of the Prepaid Insurance account shows a debit balance of $3,420 at the end of the accounting period before adjustment. Prepare journal entries to record the insurance expense for the period under each of the following independent assumptions:

a. An examination of insurance policies shows that insurance costing $1,200 has expired during the period.

b. An examination of insurance policies shows unexpired insurance of $2,640 at the end of the period.