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.
['t', '8881', 'J', 'C', 'Z', 'F', 'U', '8595', 'y', '6845', 'c', '3183', '5489', '8967', '3993', '7989', '1017', 'G', 'h', '1723']