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: [128.349, 188.471, -28.094, 47.591, -0.277, -79.911, 200.119, 211.298, -73.765]

65.976