Answer: 82
Step-by-step explanation:
The formula to find the sample size is given by :-

, where E = Margin of error.
= Population standard deviation for the prior study.
As per given , we have
gallons.
Margin of error : E= 110 gallons
Critical value for 99% confidence level = z* = 2.576
Then, the required sample size : 
{Rounded to the nearest integer.}
Hence, the minimum sample size = 82