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: [40.415, 99.494, 239.871, 249.588, -95.656, -81.967, 198.271, 66.616, -30.912, 215.106]

90.083