We would like to conduct a hypothesis test at the 5% level of signi cance to determine

whether there is evidence that the true mean age of rst-time brides in 2017 has increased

since 1997, when the true mean age was 25.4 years. We will take a random sample of

21 rst-time brides. Ages of rst-time brides in 2017 are known to follow a normal

distribution with standard deviation 2.8 years. What is the power of the test if the true

mean age of rst-time brides in 2017 is 27 years?

(A) 0.7881

(B) 0.8340

(C) 0.8962

(D) 0.9474

(E) 0.9738