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: [-10.586, 79.912, 162.956, 62.621, 20.17, 175.22, 19.366, 134.958, 136.12]

86.749