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: [-20.618, 188.082, 108.928, 56.291, 121.601, 193.406, 81.14, -60.34, 162.33, -71.764]

75.906