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: [-19.64, 5.69, 102.211, 159.062, 7.744, 242.03, 141.431, 105.364, 40.338]

87.137