write a program that calls a function calculatesum to calculate the sum from -5 to n. the function calculatesum has one parameter n of type integer and returns an integer which represents the sum from -5 to n, inclusive. write another function calculateaverage that calculates an average. this function will have two parameters: the sum and the number of items. it returns the average as a floating point number. the main function should be responsible for all inputs and outputs. your functions will only calculate and return the values and not print anything. n is provided by the user; user input must be asked for repeatedly until a non-negative integer is provided.