We know that Harmie's average 5-day natural gas usage rate is 5.9 therms/5 days.
We have to calculate the 1 day average usage rate and 8 day average usage rate.
We can calculate this by transforming the denominator from 5 days, as it is in the information given, to 1 day and 8 days respectively:
Answer: 1.18 therms / 1 day, 9.44 therms / 8 days [Option 1]