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: [120.548, 104.355, 182.892, 208.827, 78.301, 176.671, 113.25, -33.999, 207.334]

128.687