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: [220.025, 109.071, 12.909, 132.762, 42.491, 209.712, -17.547, 117.388, 0.66]

91.941