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.
['r', 't', '9367', 'C', 'N', 'R', '4785', '7587', '497', '1027', 'l', '8125', '8359', '4523', '9339', '3431', 'N', 'm', 'b', 'R']