Write a python program that prompts the user for numbers until the user enters 999. The valid numbers that they enter should be stored in a list.

Write a python program that prompts the user for numbers until the user enters 999. The valid numbers that they enter should be stored in a list.  Write a function that calculates the average of these numbers. Your function should take the list as a parameter and return the average. If the list is empty (ie. the user didn't enter any numbers), your function should return 999.  Write another function that finds the maximum of these numbers. Your function should take the list as a parameter and it should return the maximum number contained in the list. If the list is empty then it should return 999.