Some schools give an extra bonus to the grade received in AP classes.
You will write a method that will calculate a student's GPA as either weighted or unweighted depending on the parameter: isWeighted
But not all classes are AP classes so the students grades are stored in two parallel arrays:
The first array, grades contains the letter grade which translates as follows:

A - 4 points
B - 3 points
C - 2 points
D - 1 point
F - 0 points

Grades may include a + or - but it is ignored!
The second array, isAP is true if the class is an AP class.
If a class is an AP class then an extra 1 point is added to the grade's point value if the grade is a C or better.