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.
[222.437, 198.009, 41.408, 47.695, 228.724, -22.472, 159.11, 39.423]