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.

[204.196, 129.11, 102.851, 204.533, 143.912, 214.911, 89.351, 42.705, 123.403]
139.441