On July 1, 20X1, ZipCo, which uses UOP depreciation, purchases a truck for $36,000 with an estimated useful life of 60,000 miles and a residual value of $6,000. Miles driven are as follows: Year Miles 20X1 5,000 20X2 10,000 20X3 20,000 20X4 25,000 20X5 30,000 The book value of the truck on December 31, 20X3 is:

$18,500

$12,500

$20,000

$26,000