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.
['8351', 'P', 'c', '6733', '6741', 'J', '7229', '7519', '9133', 'j', 'O', 'c', 'S', '6367', '9747', 'o', 'P', '8313', '8959', '5955']