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.
['351', 'P', '1195', '6663', 'm', '7805', '3147', '1949', '6731', 'u', '8115', 'h', '451', '2883', '4921', '7637', 'L', 'E']