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.
['6557', '899', 'N', 'Y', '9423', '7219', 'A', 'd', '9705', '939', '3661', '4617', '6933', '2167', '555', '5989', 'z', '3129', '1859', 'B']