Adventure Airlines new baggage handling conveyor costs $250 000 and has a service life of 10 years. For the first six years, depreciation of the conveyor is calculated using the decliningbalance method at the rate of 30 percent. During the last four years, the straight-line method is used for accounting purposes in order to have a book value of zero at the end of the service life. What is the book value of the conveyor after seven, eight, nine, and ten years?