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.

[21.007, 48.739, -49.831, -22.699]
-0.696

[-40.246, -7.512, 174.245, -98.6]
6.972

[72.326, -74.6, 127.566, -54.848, 198.529, -44.061, -28.155]

28.108