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.
['c', 'a', 'H', '4917', '739', 'C', '6001', '2435', 'q', 'Y', 'J', 'e', 'd', 'j', 'b', '575', '2931', '8405', '9307']