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: [200.039, -28.892, 208.657, -33.337, 78.205, -77.451, 207.664]

79.269