Question 1120296
For a, all hypotheses deal with parameters mu, not with samples.
This is worded as a 2-way test, so the answer is a.

The average price of textbooks in the store is $53.12


The point estimate is the sample result or $51.12
The interval is 2.626*s/sqrt(n), the 2.626 being the t-value for df=99, 0.995.
2.626*15.6/10=SE=4.097
The interval is the sample mean +/- SE
($47.023, $55.217)
Because $53.12 is in this interval, the true value may be what was quoted and fail to reject Ho at the 1% level.