Vickers Company use the units-of-production method in computing depreciation expense. A new plant asset is purchased for $18,000 that will produce an estimated 100,000 units over its useful life. Estimated residual value at the end of its useful life is $2,000. If 7635 units were used in the first half year, the depreciation for that period would be: $1,221.50 $1,374.30 $687.15 $610.80