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: [21.298, 170.929, 134.732, 160.877, -16.716, 186.066, 128.345, 14.746, 40.859]

93.46