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.
['7419', 'Q', '5933', '6779', 'p', '7797', 'y', 'E', '1451', 'n', 'c', '491', 'N', '6959', '9477', '749', '7357', '7059', 'o']