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: [-8.6, 148.356, 21.188, 129.408, 189.687, -3.91, 102.347, -75.62, 103.278, 198.339]

80.447