Roche Bay Mining Company buys special drills for $640,000 each. Each drill can extract about 150,000 tons of ore, after which it has a $40,000 residual value. Roche Bay bought one such drill in early January 20X1. Projected tonnage figures for the drill are 70,000 tons in 20X1, 45,000 tons in 20X2, and 35,000 tons in 20X3. The drill is scheduled for sale at the end of the third year at the $40,000 residual value. Roche Bay is considering units-of-production, straight-line, or DDB depreciation for the drill.
Compute depreciation for each year under each of the three methods.