Starling Co. is considering disposing of a mechine with a book value of $20,000 and estimated remaining life of five years. The old machine can be sold for $5,100. A new high-speed machine can be purchased at a cost of 68,400 . It will have a useful life of five years and no cesidual value. It is estimated that the annual variable manufacturing costs will be reduced from $23,000 to $20,200 if the new machine is purchased. The five-year differential effect on profit from replacing the machine is a(n) a. incricase of $64,090 b. incatase of $99.300 c. decrease or $49,300 d. dcarsue of $64,090