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.
['997', '1021', 'f', '8489', '2309', '7069', 'b', 'y', 'M', '5493', '8507', 'l', '4261', '9573', '1909', '9925', '7295', '5293', '5691']