IN CODE C: Task $2$: Nested Loops and if$-$else statements $(10$ points$)$

You will write a program to help teachers caleulate their class's average. The program should be able to take multiple classes with different number of students per class $($depends on the user$),$ go through each class, get their digit grades, output the average and the letter grade on how each class performs on average.

I break the problem down into $3$ parts to get you started. The screenshot outputs are to help you understand what is expected. Each part can be built upon the previous one. You don't need to replicate it exactly.

Part $1$: One class and digit grade inputs.

Ask the user $($teacher$)$ to input the number of students in the class $(N).$

Go through each student in the class, ask for their grade $($range from $0-100).$

Print out the class's average.

Part $2$; Multiple classes allewed.

Fix the program so that it will allow you to input grades not for one class, but multiple classes.

Ask the user to input the number of classes to process.

For each class, ask the user to input the number of students.

The number of students per class can be the same or different depends on the user.

The rest should be the same.

Part $3$; Check how well the whole class behave on average.

If you get to this point, you should get the average for a class.

Depends on the average, we'tl output what letter grade the class falls in$.$ Range:

Under $60$:$F$

$60>69$:$D$

$7079$:$C$

$8089$:$B$

$90>100$:$A$

Expected Outputs $($Left: Invalid input example. Right: Final output$)$:

Invalid input

Final output

Requirements: the number of students cannot be less than $3$

if less than $3$ exit the program using exit$(0)$

you will need to import stdlib.h library on top to use exit function

No arrays allowd and no functions allowed except for printf and scanf