Question 1078507
The 99% CI is mean +/- z(0.995) sigma/sqrt(39)
(20.94, 25.06)
This is 2.576*5/sqrt(39)=2.06
20 is not in the CI
p-value will be very small.
It is <0.0002
Note: if the CI doesn't contain what is hypothesized, the p-value is less than alpha.
If the p-value is less than alpha, the CI won't contain the CI.  That is a basic check to do.