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.
['6625', '4343', 'W', 'j', '1475', 'z', '7951', 'S', 'G', 'Q', 'n', '2537', 'H', 'D', 'P', '5969', '7025']