Augment your grades.html page from Exercise 7.10 by inserting a cascading if-else statement similar to the one on the right-hand side of Figure 11.6. In addition to displaying the student's class average, the associated letter grade should also be displayed. For example, if the student's average was calculated to be 85.5, then the message displayed in the page division should be:

Your overall course average is 85.5

Letter grade: B.