Given the task definition and input, reply with output. 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.

[248.646, 18.139, -55.179, 138.121, -33.917, 57.471, 237.952, -43.899, -10.724]

61.846