On January 1, 2017, we purchased a truck for $55,000. The truck has a useful life of 5 years or 100,000 miles and a residual value of $5,000. The actual mileage for the truck was 25,000 miles in 2017 and 30,000 miles in 2018. The truck is depreciated using the units of production method. What is the balance in accumulated depreciation expense after the adjusting entry for 2018?

a. $20,000

b. $27,500

c. $22,000

d. $22,500