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.
['4387', 'j', 'o', 'q', 'a', 'i', '7085', '7943', 'K', 'y', 'N', 'W', 'S', '3425', 'w', '7733', '8505']