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.
['5087', '7857', '8841', '3005', 'l', 'h', '3551', 'J', '9317', '9683', '5245', '5261', 'P', 'P', '7509', 'a', '201', 'l', '6093', '5791']