Write a C program that defines an array of characters of size 100, the user enters the number of characters he will enter, use functions to do the following tasks: 1- Ask the user for a value and encrypt the array content with that value using addition 2- Switch the case of the characters if it's uppercase to lowercase and vise versa 3- Ask the user of a character and find the number of times it's shown in the array 4- Print the first index that this character appeared in.