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.

[238.124, 163.429, 28.738, -70.082, 86.352, 125.656, 20.404, 159.489, 27.774]
86.654