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: [-51.127, -53.399, -58.094, 172.367, -29.286, 109.468, -34.858, -99.953, 9.617, -8.063]

-4.333