Xinhong company is considering replacing one of its manufacturing machines. the machine has a book value of $45,000 and a remaining useful life of 5 years, at which time its salvage value will be zero. it has a current market value of $52,000. variable manufacturing costs are $36,000 per year for this machine. information on two alternative replacement machines follows. alternative a alternative b cost $ 115,000 $ 125,000 variable manufacturing costs per year 19,000 15,000 calculate the total change in net income if alternative a, b is adopted. should xinhong keep or replace its manufacturing machine? if the machine should be replaced, which alternative new machine should xinhong purchase?