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: [163.31, 36.308, -31.088, 13.128, 212.404, 3.921, 189.181, 213.59, 141.662]

104.713