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.

[-1.1, 165.395, -38.244, 86.12, -73.989, 148.672, -9.01]
39.692