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: [137.16, 20.778, 231.77, 58.379, 28.577, -11.863, 0.135, 33.089]

62.253