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: [146.286, -90.849, 216.772, 115.089, 6.542, -7.268, -45.921, 87.876]

53.566