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: [230.511, 82.342, -99.243, -34.634, 128.067, 115.224, 57.888, -51.674, 81.074]

56.617