In this task, you are given an input list A. You need to find all the elements of the list that are numbers and calculate their sum.
['U', 'P', '1381', 'C', 'u', '3725', '3167', 'r', 'b', 'q', 'v', '8797', 'c', 'R', '9839', 'c', 'H', 'm']