You need to compute the sample mean

and the sample variance

.

a) find the 95% confidence interval for the mean.

The interval here is

where n is the number of observations and t is a percentile point from your t table.

The degrees of freedom is n-1 (which is your row) and the column is

.

b) find the 95% confidence interval for the variances

THERE is only one variance here. The confidence interval is ...

where

has n-1 degrees of freedom and

.

while

has n-1 degrees of freedom and

.

c) with 0.01 level of significance is it justifiable to claim that there the mean is less than 3.75 hours?

Most likely, your instructor wants you to just examine whether or not 3.75 is in the interval from part (a)

That's not really right, since that was a two sided CI and this is a one sided test.

d) is there a reason to believe that the variance is equal to 1?

This sounds like a two sided test. So once you obtain the interval, all you need to do is examine whether or not it contains the value 1.