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.
['I', 'b', '5281', 'v', '437', '5403', '5275', 'G', 'm', 'h', 'B', '9821', '247', '9919', 'O', 'K', '253', 'X', '6765', 'P']