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.
[-47.011, 188.981, 162.934, 78.594, 20.617, 176.363, 118.07, -50.264, 202.433, 249.137]