Definition: In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.
Input: [248.59, -78.396, 13.022, 0.79, 194.759, 112.156, 17.217, 209.386, -1.716]

79.534