Hypothesis testing Help

#1
Help!! Got a problem I'm trying to work out and could use your assistance....

"Hypothesis Testing
3. The director of admissions at the University of Maryland, University College is concerned about the high cost of textbooks for the students each semester. A sample of 20 students enrolled in the university indicates that X (bar) = $315.4 and s = $43.20.
a. Using the 0.10 level of significance, is there evidence that the population mean is above $300?
b. What is your answer in (a) if s = $75 and the 0.05 level of significance is used?
c. What is your answer in (a) if X (bar) = $305.11 and s = $43.20?
d. Based on the information in part (a), what decision should the director make about the books used for the courses if the goal is to keep the cost below $300?


What I THINK I know so far....

Null Hypothesis: H0<= 300
Alternate Hypothesis Ha>300
Std Dev: 43.20
Significance Level .10
x(bar)=315.40
n=20
df=19

I've been doing some confidence interval problems and I can't seem to figure out if I have to do some work with a confidence interval before I work on the hypothesis test...???