This question is incomplete , l can’t answer it . You have to say how much minutes or hours they work to get paid $40 ,if you just say that John’s work one hour and Mike work 1.5 hours then I don’t know what to solve ,this question is a complete
301 is the correct answer:)
Given that the standard deviation, s = 2.3 and that there are 24 students, thus the degree of freedom is 24 - 1 = 23.
For 90% confidence interval,

and

From the chi-square table, the value of

and the value of

.
The 90% confidence interval for

is given by:

And the 90% confidence interval for

is given by: