An oil company claims that the sulfur content of its diesel fuel is at most .15 percent. To check this claim, the sulfur contents of 40 randomly chosen samples were determined; the resulting sample mean and sample standard deviation were .162 and .040.

(a) Calculate the p-value needed to test whether the company’s claim is valid.
(b) Use part (a) to conclude the test at the 5 and 10 percent levels of significance.