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: [-3.315, 153.889, 208.841, 240.33, 222.577, 131.967, 33.853, -91.672, 40.029]

104.055