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.
['3685', 'S', 'U', '8413', 'b', '7707', 'U', '9165', '9101', 'j', 'W', 'K', 'm', 'r', 'o', '8323', 'A', '353', '3799', '3183']