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: [217.865, -38.125, 82.461, -28.299, 219.556, 155.171, -16.325, 118.055, -26.605, -91.388]

59.237