Swifty Corporation purchased a new machine for its assembly process on August $1,2020.$ The cost of this machine was $$125,100.$ The company estimated that the machine would have a salvage value of $$17,100$ at the end of its service life. Its life is estimated at $5$ years, and its working hours are estimated at $20,000$ hours. Year$-$end is December $31.$

Compute the depreciation expense under the following method Each of the following should be considered unrelated $($Round depreciation rate per hour to $2$ decimal places, e$.$g$.5\mathrm{.}35$ for computational purposes. Round your answers to $0$ decimal places, e$.$g$.45,892.)$

$($a$)$ Straight$-$line depreciation for $2020$

$($b$)$ Activity method for $2020,$ assuming that machine usage was $830$ hours $

$($c$)$ Sum$-$of$-$the$-$years'$-$digits for $2021$

$($d$)$ Double$-$declining$-$balance for $2021$