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: [239.856, 55.271, -85.733, 237.012, -58.101, 214.516, 107.481, 156.275]

108.322