A student of journalism is curious about the average rates paid to freelancers by online magazines. She takes a random sample of 51 online publications and computes a mean rate per word of 13 cents, with a sample standard deviation of 4.2 cents. The student wants to use this sample information to find a 90% confidence interval for the average pay rate per word.

(a) What is the critical t-value that will need to be used to calculate the confidence interval?

(b) What is the 90% confidence interval?