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.