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: [-86.758, -73.21, 229.928, 127.151, 228.62, -90.768, 28.252]

51.888