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.
['9467', 'A', '3803', '693', 'z', '9693', '6275', '8481', '8921', '8005', 'L', 'O', '4309', '7049', 'S', 's', 'u', 'c']