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: [139.244, 184.59, 132.272, -57.545, 148.006, 242.409, 236.896, -2.984, 79.723]

122.512