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: [213.217, -36.92, 166.187, 199.664, 222.995, 60.119, 46.382, 6.489, 30.734]

100.985