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.
['t', '3257', '9607', 'v', '2879', '3011', '973', '1191', 'Q', 'A', '6659', '1735', 'e', 'e', '6915', 'b', '6685', '5983', '5759', 'u']