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: [198.488, -82.309, 221.856, -62.11, -56.522, 179.093, 187.819, 146.271, 38.546]

85.681