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.
[247.931, 34.114, 140.132, -60.779, 111.539, 94.932, 80.318]