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: [198.239, 45.107, 121.978, 18.939, 26.34, 44.343, -90.294, 104.135, -25.865]

49.214