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: [136.986, -72.697, -9.581, -44.692, 79.9, 68.205, 103.108, 18.406, 89.891, -31.264]

33.826