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.

Example Input: [78.523, 239.098, 9.698, 69.94]
Example Output: 99.315

Example Input: [207.804, 175.122, 13.63, 217.625, -98.484]
Example Output: 103.139

Example Input: [-60.505, -96.74, -6.839]
Example Output:
-54.695