A residential building is heated with a 78 percent efficient gas-fired furnace (costing $1,600). The annual heating load is estimated at 160 MMBtu. The cost of gas is $6.00/ MMBtu. For the discount rate of 5 percent and a 10-year cycle, determine:
(a) The life cycle of the existing heating system
(b) If it is worth considering a 90 percent efficient gas-fired furnace that costs $2,800
(c) The variation of the life-cycle cost savings between the two systems [the existing system and that proposed in (b)] versus the life of the system for life cycles ranging from 3 to 20 years Conclude.