A company plans to replace an aging machine in 8 years. The new machine should cost about $108,157. The old machine should also have a $4,002 trade-in value. For now, they make process changes that save $402 a month in operating costs. They plan to invest the savings each month at a nominal 8.86%, compounded monthly. They do not want to finance the new machine. To do this, how much more must they save per month