2. Functions with Array Parameters (*)
Write a function that takes an array of positive integers and the size of the array, and returns the average (type float) of the values. Test your function with a main function, that reads in an array of positive integers (it stops reading when it sees a negative number), passes the array and its size to your function, and prints the resulting average.
3. Functions with String Parameters (*)
Write a function that takes three strings as input and returns a string equal to the concatenation of the three strings in alphabetical order. Test your function with a main function.