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: [54.181, 68.195, 123.555, 158.006, 177.509, 10.3, -89.165, 144.033, 238.952, -66.686]

81.888