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: [-80.155, 77.691, 229.301, -44.331, -32.834, -20.125, 241.433, 73.598, 40.039]

53.846