Electricity wasn't the only energy cost. also look at logs for fire. being that they were bought for fire it is using heat energy. there for making the total energy cost the highest. only look at what is energy cost toward the overall bill.
Would it not just be q? Since I am assuming that 1.025 is the interest rate of the bank hence why it would be multiplied by the year.
(a + b)^3 = a^3 + 3a^2b + 3ab^2+ b^3
(a +(- b))^3 = (a-b)^2 = a^3 - 3a^2b + 3ab^2- b^3
