Bob starts selling extended warranty for type S on July 1, Year 8 for the lawn mower whose original warranty expired. The company charges $500 for additional two years of warranty service and it expects to incur $400 over the two-year period. From July 1 to December 31, Year 8, the company sells 100 extended warranties and it incurs a total of $12,000 for repairs specifically related to extended warranty. Bob follows revenue approach for the extended warranty. (2) Determine the balance of unearned warranty revenue at December 31, Year 8.