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: [155.964, -16.379, 240.539, 90.653, 79.615, 169.355, 179.188, 242.35, 102.16]

138.161