Answer:
The value of test statistic is -4.1247
Step-by-step explanation:
We are given the following in the question:  
Population mean, μ = $3.26 a gallon
Sample mean,  = $3.19 a gallon
 = $3.19 a gallon
Sample size, n = 32
Sample standard deviation, σ = $0.096
First, we design the null and the alternate hypothesis
 
 
We use one-tailed t test to perform this hypothesis.
Formula:
 
 
Putting all the values, we have 
 
 
Thus, the value of test statistic is -4.1247