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: [128.6, 5.116, 6.059, -98.416, -95.267, 43.438, 90.988, 240.489, -45.447]

30.618