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: [199.418, -21.567, 190.596, 58.811, 13.714, 138.895, 118.257, -12.757, -98.956]

65.157