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.

Example Input: [199.874, -45.634, -39.343, 75.985, 143.35, 87.15, 120.645, -34.636, 159.567]
Example Output: 74.106

Example Input: [-19.13, 98.86, 158.686, 230.23]
Example Output: 117.161

Example Input: [20.002, 82.676, -51.919, 187.974, -25.189, 142.125, 202.897, 109.952]
Example Output:
83.565