On January 1, 2025, a company acquired a truck for $50,000. Residual value was estimated to be $10,000. The truck can be driven for 130,000 miles or a useful life of four years. Actual usage of the truck was recorded as 9,000 miles for the first year and 11,000 miles for the second year. The book value at the end of year 2, calculated by the units-of-production method is _________?