Alexander and Thomas Grey, both business students from Harvard University, want to invest further cash in their successful vending machine operation on the university campus. They plan to introduce new vending machines with health foods at the total cost of $18,000. They estimate that set-up and delivery costs would be equal to an additional $2,000. According to their financial projections incremental sales would increase by $15,000 per annum in the first two years, and then begin to decline in subsequent years as the novelty of these machines wear off (year 3 - $10,000; year 4 - $8,000; year 5 - $6,000). The increase in operating expenses is estimated to be 30% of the annual change in sales. With this purchase