1. Write a C++ program for a simple calculator using switch statement, that takes an arithmetic operator (+, -, *, /) and two operands from an user and performs the operation on those two operands depending upon the operator entered by user.
2. Write a program that determines a students grade. The program will read average score from the user and determine the grade based on the following rules:

-if the average score =90% =>grade=A

-if the average score >= 70% and <90% => grade=B

-if the average score>=50% and <70% =>grade=C

-if the average score<50% =>grade=F

3. Write a C++ program with an user-defined function Sum, which adds two input numbers from the user and print the output.