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: [164.647, 208.487, 225.23, -9.837, 75.508, 231.456, 21.172, -77.569, 4.399]

93.721