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.
[-66.407, 201.345, 121.728, -72.505, 65.694, 204.744, 23.038]