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.
Q: [-28.86, -28.932, 8.45, -10.892, 79.215, -13.716, -16.466, -76.434, -3.226]
A: 
-10.096