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: [-74.318, 134.526, 111.234, 221.516, 216.098, 46.965, 20.36, -84.978, 194.799]

87.356