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.
['5863', '3587', 'M', 'e', '645', '8445', '9987', 'K', '7771', 'C', '7043', '9775', 'd', '3905', 'v', 'x', '5499', '3671', '4429']