Starling Co. is considering disposing of a machine with a book value of $20,000 and estimated remaining life of five years. The old machine can be sold for $5,900. A new high-speed machine can be purchased at a cost of $70,900. 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 $23,400 to $19,100 if the new machine is purchased. The differential effect on income for the new machine for the entire five years is a(n)

a.increase of $56,550

b.increase of $43,500

c.decrease of $56,550

d.decrease of $43,500