Just 9.26 a, with steps so I can understand

b. Test the hypothesis of part a using the critical-value approach and a = .025. 9.26 According to the U.S. Bureau of Labor Statistics, all workers in America who had a bachelor's degree and were employed earned an average of $1224 a week in 2014. A recent sample of 400 American workers who have a bachelor's degree showed that they earn an aver- age of $1260 per week. Suppose that the population standard devia tion of such earnings is $160. a. Find the p-value for the test of hypothesis with the alternative hypothesis that the current mean weekly earning of American workers who have a bachelor's degree is higher than $1224. Will you reject the null hypothesis at a = .025? b. Test the hypothesis of part a using the critical-value approach and a = .025