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: [58.578, 228.252, 240.764, -56.071, 11.356, 179.293, -40.022, 41.436, 142.424]

89.557