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.
['7403', '6363', 'q', '3707', 'l', '9669', '4239', '1219', 'c', '5377', 'V', '9753', '2869', '2721', 'g', 'y', 'p', 'X']