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.
['p', '5237', 'i', 'M', 'k', 'K', 's', '2509', 'f', '5709', '6571', 'u', 'H', '7203', 'x', '2929', 'h', '4675']