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.
['E', '83', 'F', '4787', '1567', '87', '1497', 'z', '3017', 'U', 'p', '9977', 'X', '2879', 'o', 'I', '4711', '9127', '4273', 'b']