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: [137.406, 41.059, -11.091, 34.113, 193.319, 111.42, 36.348, 39.746, 204.726, -42.921]

74.412