On December 31, 2012, Oakbrook Inc. rendered services to Begin Corporation at an agreed priceof $102,049, accepting $40,000 down and agreeing to accept the balance in four equal installments of $20,000 receivable each December 31. An assumed interest rate of 11% is imputed.

Instructions
Prepare the entries that would be recorded by Oakbrook Inc. for the sale and for the receipts and interest on the following dates. (Assume that the effective-interest method is used for amortization purposes.)

(a) December 31, 2012.
(b) December 31, 2014.
(c) December 31, 2016.
(d) December 31, 2013.
(e) December 31, 2015.