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 25 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?