(A) an Old 68% Efficient Natural Gas Furnace Is Used $\mathrm { CO } _ { 2 }$

Essay

(a) An old 68% efficient natural gas furnace is used to heat a 400 m³ home in Boston, MA. Estimate the annual savings in $\mathrm { CO } _ { 2 }$ emissions if the furnace is replaced with a $93 \%$ efficient natural gas furnace?
(b) Estimate the annual $\mathrm { CO } _ { 2 }$ savings if the old furnace is replaced with an $80 \%$ efficient