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.
['X', 'P', 'x', '9471', '5', 'c', 'f', '5077', '1085', '2267', 'R', 'q', '4987', '9529', 'H', 'n', 'r', 'u']