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.
['s', '407', '7983', '1523', '8983', '9841', 'p', 'y', 'N', '7633', 'T', '4177', 'Z', 'Y', '3223', '7125', '2601', '7467', '3039']