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.

[99.431, -0.986, -97.815, 83.097, 183.282, 61.416, -26.114, -8.399, -8.236, -67.816]
21.786