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: [64.991, 221.636, -32.654, 160.852, -48.12, 176.115, 223.483, 51.997, 99.053, -69.184]

84.817