On January $1,20$X$1,$ Slim Inc. purchased machinery for $$350,000.$ The machinery had an estimated useful life of $10$ years and a salvage value of $$35,000.$ The company elected to use sum$-$of$-$years digits depreciation. At the beginning of $20$X$5,$ Slim decided to$,$ switch to the straight$-$line method of depreciation and reassessed the remaining useful life of the machinery to be $4$ years with no change in the salvage value. A change in depreciation methods together with a change in the useful life of the asset is

a change in accounting principle effected as a change in accounting estimate.

a change in accounting estimate.

an error correction.

a change in accounting principle.