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: [76.134, 239.206, 80.097, 88.585, 202.486, -27.557, 148.626, 215.947, -73.118, -80.315]

87.009