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.

[70.748, 145.924, 213.55, -15.446, 219.555, 89.961]
120.715