Quick-as-Lightning, a delivery service, purchased a new delivery truck for $40,000 on January 1, 2019. The truck is expected to have a useful life of ten years or 150,000 miles and an expected residual value of $3,000. The truck was driven 15,000 miles in 2019 and 13,400 miles in 2020.

1. Calculate the depreciation expense for 2019 and for 2020 under the straight-line method.

2. Calculate the depreciation expense for 2019 and for 2020 under the double-declining balance method.

3. Calculate the depreciation expense for 2021 under the double-declining balance method.