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.
[-67.543, 138.788, 83.985, 131.939, 136.817, 176.185, 131.14]