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: [-57.016, 175.989, 132.392, 217.191, 102.575, 192.182, 214.864, 30.191, 138.432]

127.422