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.
['2613', 'W', '9411', '8099', 'w', '2973', '6023', 'D', 'j', '6815', '3707', 'H', '7567', 'T', 't', 'w', '2441', '705', '3467', 'b']