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', '91', '4805', '7911', '9349', '5113', 'o', 'p', 'E', 'L', 'x', '1121', 'y', 'C', 'a', 'T', '9587', 'u']