1.Suppose that we wish to predict the credit rating transition for a corporation over the next year. The corporation's credit rating can be upgraded, downgraded, or it can remain unchanged. We are using the corporation's Debt-to-EBITDA ratio to predict the likelihood for the transition. We examine a large number of corporations and discover that the mean value of Debt-to-EBITDA ratio for corporations that had their credit rating upgraded was, the mean of Debt-to-EBITDA ratio for corporations that had their credit rating downgraded was, while the mean for those, whose credit rating didn't change was. In addition, the variance ofXfor these three sets of corporations was. On average, 30% of corporations have their credit rating upgraded and 20% of corporations have their credit rating downgraded. Assuming thatthe Debt-to-EBITDA ratiofollows a normal distribution, predict the probability that a corporation will have its credit rating upgraded this year, given that its Debt-to-EBITDA ratio was 0.45 last year.