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.
['6625', 'Y', 'n', 'D', 'j', '1553', 'G', '2703', 'O', 'l', 'T', '3681', 'X', '7893', '3803', 'd', '8517', 'P', 'E']