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: [-40.416, -24.51, 13.291, 245.866, 102.777, 136.082, 89.702, 246.627, 206.586]

108.445