Explain the concept of self-interest and that decisions of what people choose to provide a society (such as types of products that they choose to produce) will not be based on what is best for society but what will profit the individual and help him/her to accomplish their economic goals and make the most money.

Xinhong company is considering replacing one of its manufacturing machines. the machine has a book value of $39,000 and a remaining useful life of 5 years, at which time its salvage value will be zero. it has a current market value of $49,000. variable manufacturing costs are $33,300 per year for this machine. information on two alternative replacement machines follows. alternative a alternative b cost $ 115,000 $ 117,000 variable manufacturing costs per year 22,900 10,100 1. calculate the total change in net income if alternative a and b is adopted. 2. should xinhong keep or replace its manufacturing machine