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: [2.258, 234.144, 166.894, -75.514, -15.024, -48.211, -21.893, 66.767, -9.283, -11.226]

28.891