Two heat transfer units are being evaluated for purchase. The costs and other data for the purchase are as follows: a. Determine the incremental present worth (B-A) for these investments and select the least cost unit. b. Determine the sensitivity of the decision to the purchase cost by finding the difference in the purchase cost of unit A that would be needed to change the selection of the alternatives. c. Do the same with the operating costs. How much would the AOC of unit A have to increase or decrease to change the alternative selection