Carleton Corporation, which uses a calendar year fiscal year, purchased a piece of equipment for $50,000 on January 3, 2017. It estimates the equipment will have an estimated useful life of 8 years and a $4,000 residual value. The equipment is used to produce 200,000 units during its useful life. The actual number of units produced was 20,000 during 2016; 33,000 during 2018; 18,000 during 2019; and 28,000 during 2020. Using the units-of-production method, what is the accumulated depreciation at December 31, 2020?