Starling Co. is considering disposing of a machine with a book value of $24,500 and estimated remaining life of five years. The old machine can be sold for $5,600. A new high-speed machine can be purchased at a cost of 68,200 . It will have a useful life of five years and no residual value. It is estimated that the annual variable manufacturing costs will be reduced from $22,600 to $19,300 if the new machine is purchased. The five-year differential effect on profit from replacing the machine is a(n) a. decrease of $46,100 b. increase of $59,930 c. increase of $46,100 d. decrease of $59,930