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: [-20.087, 190.801, -33.07, -46.781, 179.593, 239.585, 15.6, 82.728, -99.69, 237.17]

74.585