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: [-87.239, 176.019, -5.769, -11.992, 180.644, -27.711, -85.106, 140.235, 100.673]

42.195