Answer:
The value of the test statistic is 
Step-by-step explanation:
The null hypothesis is:

The alternate hypotesis is:

Our test statistic is:

In which X is the sample mean,
is the value tested at the null hypothesis,
is the standard deviation and n is the size of the sample.
In this problem, we have that:

Then



The value of the test statistic is 
15/60 simplified is 1/4
1/4 is not equal to 3/4
28.50x + 110.99(14-x)=811.45
distribute
28.50 x + 1553.86-110.99x =811.45
combine like terms
-82.49x+1553.86=811.45
subtract 1553.86 from each side
-82.49x =-742.41
divide by -82.49
x=9
He bought 9 of the 28.50 features and 5 of the 110.99 features
I'm pretty sure that it would be 1/2 since it says 1/3 each whole, which in this case it would be 1/3 each hour.