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: [-97.561, -98.725, -99.064, -71.908, 181.665, 57.646, 127.671, 58.021, -88.789, 245.506]

21.446