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.
['8693', '5839', 'v', '8289', '5637', 'R', '8837', '2325', '8965', '7235', 'X', 'V', '7139', 'S', 'j', 'I', 'K', '6907', 'D']