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.
['D', 'O', 'o', 'Z', 'k', '5705', '9', '2689', '9925', '9145', '9439', 'f', 'x', '2867', '6597', '9605', '5625', 'D']