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.
['6189', 'J', '7973', '9331', 'e', 'K', '9843', 'q', 'A', '4987', '5309', '7033', '4341', 'l', '3797', 'V', 'B', 'P', 'S']