I have the answer below but I have just one equation. from where and how they got the 20000 ( I underline it below)

In recent years Button Ltd has purchased three machines. Because of frequent employee turnover in the accounting department, a different accountant was in charge of selecting the depreciation method for each machine, and various methods have been used. Information concerning the machines is summarised in the table below Machine Acquired Cost Residual value Useful life Depreciation method (in years) 1 Jan 2015 $54,000 $10,500 10 Straight-line 1 Jan. 2016 $38,400 $9,000 Diminishing-balance 1. Jan 2016 $25,000 $6,000 5 Units-of-production * Diminishing-balance method rate of depreciation is 1.5 x straight-line rate for the same asset. For the units of production method, total machine hours are expected to be 10 000. Actual hours of use in the first 3 years were: 2016, 1000; 2017, 3000, and 2018, 4000. Required a. Calculate the amount of accumulated depreciation on each machine at 31 December 2018 .. . L o thodir baraforrad method for tay Button Ltd Balance date 31 December Accumulated Depreciation 31/15 Year 2015 2016 2017 2018 Calculation MACHINE 1 $43,500 X 10% = $4,350 $43,500 X 10% = $4,350 $43,500 X 10% = $4,350 $43,500 X 10% = $4,350 $4,350 8,700 13,050 17,400 2016 2017 2018 MACHINE 2 $38,400 x 18.75% = $7,200 $31,200 x 18.75% = $5,850 $25,350 x 18.75% = 4,753(rounding) $7,200 13,050 17,803 2016 2017 2018 MACHINE 3 1,000 X $2.00 = $2,000 3,000 x $2.00 = $6,000 4,000 x $2.00 = $8,000 $2,000 8,000 16,000 $20,000 + 10,000 hours = $2.00 per machine hour