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: [-27.872, -9.249, 218.646, -32.0, 49.715, 58.225, 118.489, 29.679, 31.407]

48.56