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: [-87.538, -7.561, 26.601, 135.996, -42.301, 225.007, 144.611, -15.788]

47.378