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: [200.059, 99.343, -92.615, 112.717, 121.777, 163.537, 144.178, 193.189, 248.859, 171.337]

136.238