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.

[-76.417, 184.497, 170.684, -35.367, 45.159, 207.202, 109.671]

86.49