Allison's math class found that it would take 1.5E7 Artifical Field grass to cover a square mile area. The surface area of the United States is about 2.8E8 square miles. About how much Artifical field grass is needed to cover the United States? A. 4.0E19
B. 4.2E23
C. 5.0E17
D. Other

An automobile assembly line operation has a scheduled mean completion time, μ, of 12 minutes. the standard deviation of completion times is 1.6 minutes. it is claimed that, under new management, the mean completion time has decreased. to test this claim, a random sample of 33 completion times under new management was taken. the sample had a mean of 11.2 minutes. assume that the population is normally distributed. can we support, at the 0.05 level of significance, the claim that the mean completion time has decreased under new management? assume that the standard deviation of completion times has not changed.