On July 1, 2022, Duncan Inc. purchased equipment for $56 , 000 . The equipment had an estimated life of ten years, an estimated residual value of $8 , 000 , and was expected to be used to produce 150,000 units over its life. During 2022 , the equipment was used to produce 9,000 units and during 2023 it was used to produce 17,000 units. Assume Duncan, Inc. uses the units of production method to depreciate its assets. Calculate the equipment's book value at December 31 , 2023