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.
['e', 'U', 'F', '363', '3815', '4161', '8275', 'h', '2437', 'e', 'A', '3441', '4403', '3271', '4781', 'B', '6387', 'k']