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: [133.842, 101.473, 152.47, -21.724, 61.343, -38.845, 138.237, -35.055, 76.845]

63.176