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.
['U', 'y', 'z', 'w', 'q', 'W', 's', 'o', '2933', '7417', 'T', '8733', '5437', '493', 'v', 'C', '7797', 'v', 'Q', 'B']