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.
['W', '4683', '1253', '1751', '4957', '5417', '7577', 'e', 'J', '1667', '955', 'b', '3239', 'w', 'a', '69', 'I', '4391']