A GPA, or Grade point Average, is calculated by summing the grade points earned in a student’s courses and then dividing by the total units. The grade points for an individual course are calculated by multiplying the units for that course by the appropriate factor depending upon the grade received:

```
A receives 4 grade points
B receives 3 grade points
C receives 2 grade points
D receives 1 grade point
F receives 0 grade point
```

Your program will have a while loop to calculate multiple GPAs and a while loop to collect individual grades (i.e. a nested while loop).

For your demo, calculate the GPA to 2 decimal places for these two course combinations:

```
First Case: 5 units of A 4 units of B 3 units of C
Second Case: 6 units of A 6 units of B 4 units of C
```

I have no idea what to do.