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: [77.558, 212.183, 22.334, -13.652, 179.857, 11.818, -55.27, 238.171, -7.472]

73.947