On June 30. 2017 the company received $1,500 in advance on a sales contract that requires the company to deliver supplies at the end of each quarter valued at $375 for the next four quarters. The accountant incorrectly recorded the entire amount as revenue on June 30, 2017. Goods have been delivered as stipulated in the contract on September 30 and December 31. What would be the adjustment to unearned revenue to remedy this error on December 31, 2017, assuming the books have not yet been closed for 2017