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.
['7551', 'h', '2605', '8455', '1547', 'p', '6049', '6981', '8115', '5609', 'B', '7483', 'h', 'L', 'g', 'b', 'U', '9811', '6525', '5003']