Definition: 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.
Input: [105.19, -19.03, -21.673, 142.086, 100.97, 172.364, -74.976, -63.524]

42.676