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: [199.874, -45.634, -39.343, 75.985, 143.35, 87.15, 120.645, -34.636, 159.567]

74.106