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.
['f', '1793', 'k', '2621', '3703', 'X', 'L', 'z', 'F', 'e', 'K', 'w', 'C', 'M', '2847', '5043', 'h', '385', '7699']