PROBLEM 6. The National Center for Education Statistics (NCES) is interested in the average length of time it takes college students to earn a bachelor's degree. From previous experience NCES believes that the standard deviation of the length of time is 1.68 years. Answer the following questions. (Round your boundaries to 2 places after the decimal point).

Question 9 (1 point): A random sample of 64 college graduates yields the average length of time to earn a bachelor's degree of 4.96 years. Construct a 98% confidence interval for the average length of time it takes college students to earn a bachelor's degree.

a) (4.55, 5.37) years

b) (4.47, 5.45) years

c) (4.61, 5.31) years

d) None of the above