Modify Lab Five such that you use functions for each math calculation (Add, Subtract, Multiply, and Divide). Pass in parameters to each function for the values to use and the functions will return the result. Use a function to read in the numbers involved. These numbers will be doubles. Also write a function that reads in the operator and returns a boolean - true if the operator is valid, false if not valid. This function will have two parameters. First is a string of characters containing the valid operators. The second is a reference parameter where the operator will be placed if the operator entered is valid.