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: [-9.476, 205.539, -33.277, -84.779, 21.447, -86.155, -94.619, -23.898, 207.151, 209.915]

31.185