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.
['9039', '3105', 'n', '6479', '9705', '6305', 'v', 'Q', '1421', '4481', 'B', 'W', 'Q', 'T', '8991', '6295', 'M', '625', '2527', '341']