C++ Language only please!!

Write a program that calls a function calculateSum to calculate the sum of N integers. The function calculateSum has one parameter n of type integer and returns an integer which represents the sum from 0 to N, inclusive. After calculating the sum of this N numbers write a function that calculate the average. This function will have three parameters: the sum, the number of items and the average. This function should calculate and return the average through one of its parameters (passing parameters by reference). The main function should be responsible for all print-outs. In other words, your functions will only calculate and return the values and NOT print anything