Guardian is a national manufacturing company of home health care appliances. It is faced with a make-or-buy decision. A newly engineered lift can be installed in a car trunk to raise and lower a wheelchair. The steel arm of the lift can be purchased for $0.60 per unit or made inhouse. If manufactured on site, two machines will be required. Machine A is estimated to cost $18,000, have a life of 6 years, and a $2000 salvage value; machine B will cost $12,000, have a life of 4 years, and a $500 salvage value (carry-away cost). Machine A will require an overhaul after 3 years costing $3000. The AOC for A is expected to be $6000 per year and for B $5000 per year. A total of four operators will be required for the two machines at a rate of $12.50 per hour per operator. One thousand units will be manufactured in a normal 8-hour period. Use an MARR of 15% per year to determine the following:   a. Number of units to manufacture each year to justify the in house (make) option.   b. The maximum capital expense justifiable to purchase machine A, assuming all other estimates for machines A and B are as stated. The company expects to produce 125,000 units per year.