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.

[-1.31, 169.522, -26.172, 111.289]
63.332

[242.148, 97.472, -15.031, 246.784, 54.233, -27.114]
99.749

[21.531, 221.161, -31.194]

70.499