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: [-27.223, 144.738, 134.533, 213.727, -72.707, 61.629, -96.294, 94.71, -61.109]

43.556