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: [-56.965, 152.236, -42.308, 198.276, 104.282, 90.876, -51.888, 161.115, 193.887]

83.279