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: [199.974, 2.205, 197.996, 172.426, 182.153, 42.045, 53.238, 18.021, 83.903]

105.773