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: [-78.93, 108.423, 130.267, 151.071, 26.576, -72.559, 72.839, 161.747, 216.061]

79.499