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.
['r', 'Y', 'U', 'a', 'E', '9523', '671', 'S', 'T', '5273', '5705', '8533', '8371', '2323', '8945', 'Z', 'j', 'b', 'h', 'g']