Answer:
$135.70
Step-by-step explanation:
First step is to calculate the daily consumption for this family of four. We'll assume they're all in age to use and flush the toilet themselves (no babies).
So, one person flushes 9.1 gallons a day, a family of 4 would then flush 4 times that:
daily family flushes = 9.1 gal/person * 4 persons/family = 36.4 gal/family
That's for one day... now for a year...
yearly = 36.4 gal/day * 365 days/yr = 13 286 gal/year
Let's convert those gallons into cubic feet:
13 286 gal / 7.48 gal/ft³ = 1,776.2 ft³
Then we multiply the gallons by the price for 100 cubic feet and divide by 100:
1,776.2 ft³ * $7.64 /100 ft³ = $135.70