Definition: 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.
Input: [132.674, -31.96, 241.18, 242.626, 214.009, 240.556, 7.221]

149.472