A new van costs $25,000, has an estimated useful life of five years and an estimated salvage value of $5,000 at the end of that time. It is expected that the van will be driven 100,000 miles during its useful or service life. The Nation Express Company purchases this van on April 1, 2019. During 2021 the van is driven 13,000 miles and during 2022 it was driven 21,000 miles. Required: 1. Calculate the depreciation expense for 2021 and 2022 using: a. Straight-line b. Double-declining-balance c. Units-of-production