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.
['1515', '2473', '2469', '6139', 'Y', 'q', 'F', '7193', 'q', '9185', 'c', 'b', 'V', '7231', '1789', '399', '3293', '937']