3-5. The proposed small office building in Example 3-2 had 24,000 net square feet of area heated by a natural gas furnace. The owner of the building wants to know the approximate cost of heating the structure from October through March (6 months) because she will lease heated space to the building’s occupants. During the heating season, the building will require roughly 60,000 Btu per cubic foot of heated area. Natural gas has 1,000 Btu per cubic foot, and natural gas costs $10.50 per thousand cubic foot. What will the owner pay to heat her building? (3.3)