A university wants to know if the average salary of its graduates has increased since 2015. The average salary of graduates prior to 2015 was $48,000. Since 2015, the university surveyed 256 graduates and found an average salary of $48,750. Assume that the standard deviation of all graduates' salaries is $7,000. a. Specify the null and alternative hypotheses to determine whether the average salary of graduates has increased. . Calculate the value of the test statistic and the p-value at a 5% significance level. At the 5% significance level, can you conclude that salaries, on average, have increased? Explain