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.
['4009', 'C', '7413', 'P', '2079', '8895', 'c', 'g', '1269', 'j', '2949', '207', '3711', 's', 'q', '7391', 'b', 'x', 'B']