A 110,000ft2 commercial building has an energy requirement of 115 kBTU/ft2/y for heat and hot water in the form of natural gas. The gas costs $8.50/MMBTU and emits 117lb. of CO2 per MMBTU. The owner is considering an energy conservation retrofit costing $300,000 and reducing annual natural gas consumption by 20%. How many tons of CO2 does the investment save per year? Do the calculations and choose the nearest correct answer. 23 43 112 56