C++ show all steps please with explanation

Question 3: [50 points Write a complete CH program which will compute a grade point average (gpa) using the follow- ing formula: gpa- creditvalue X gradepoint creditvalue In this formula, n specifies the number of courses, creditvalue specifies the credit value associated with a particular course, grade point specifies the grade points for the course. The program should prompt the user to enter the number of courses. The program then continues and inputs the letter grade and credit value of each course and computes the grade point average. We will assume (for sake of simplicity) that the only possible letter grades are A,B,C,D, and F. The correspondence between a letter grade and gradepoint value is given by: A = 4.3 B=3.0 C = 2.0 D=1.0 F = 0.0 Typical user interaction with the program would be as follows: Enter the number of courses taken: 3 Enter the letter grade and the credit value for a course: A 3.75 Enter the letter grade and the credit value for a course: B 3.0 Enter the letter grade and the credit value for a course: C 3.0 Your GPA for this term is 3.19231