Darcelle Enterprises purchased a delivery van for $30,000 on January 1, 2007. The van was estimated to have a service life of five years and a residual value of $6,000. The company is planning to drive the van 20,000 miles annually. Compute depreciation expense for 2008 by using each of the following methods: a. Units-of-output, assuming 17,000 miles were driven during 2008 b. Straight-line c. Double-declining balance