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: [133.309, 99.886, 83.459, -20.236, 100.458, -42.182, -10.716, -6.752]

42.153