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: [218.725, 201.379, 122.525, -52.685, 31.401, 209.371, 215.647, 208.345, 135.43, 135.002]

142.514