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: [117.198, 217.045, 10.449, 108.17, -54.738, 215.326, 4.34, 12.791]

78.823