Reconsider Prob. 2-59E. Using EES (or other) software, study the effects of the unit cost of energy, the new combustion efficiency on the annual energy, and cost savings. Let the efficiency vary from 0.7 to 0.9, and the unit cost to vary from $4 to $6 per million Btu. Plot the annual energy and cost savings against the efficiency for unit costs of $4, $5, and $6 per million Btu, and discuss the results.