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: [144.186, 111.502, 209.899, -66.28, 92.01, 134.181, -96.324, 69.264, 181.687]

86.681