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: [21.331, -96.267, 232.248, -46.94, 11.743, 73.872, 228.407, 129.412, 32.276]

65.12