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.
['3981', '8959', 'b', 't', 't', 'q', '1691', '1741', 'g', '2887', 'h', 's', 'f', 'p', '9263', 'd', 'D', '2129', 'D']