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: [39.222, -61.519, 103.3, -72.407, 198.299, 99.057, 228.194, 204.841, 134.64, -71.826]

80.18