(GradeBook Modification) Modify the GradeBook program of Figs. 1-3 to calculate the grade-...

(GradeBook Modification) Modify the GradeBook program of Figs. 1-3 to calculate the grade-point average. A grade of A is worth 4 points, B is worth 3 points, and so on.

Fig 1. GradeBook class definition that counts letter grades.

Fig 2. GradeBook class uses switch statement to count letter grades. (Part 1 of 3.)

Fig 2. GradeBook class uses switch statement to count letter grades. (Part 2 of 3.)

Fig 2. GradeBook class uses switch statement to count letter grades. (Part 3 of 3.)

Fig 3. Creating a GradeBook object and calling its member functions.