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.
['y', 'Z', '3267', '3715', '149', 'a', '8963', 'Q', '3323', 'P', '6849', '2495', '2781', 'h', 'u', '1589', '9877', 'd']