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: [99.171, 17.131, 87.99, 101.136, 99.884, 238.408, 7.495, -35.896, 63.328]

75.405