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.
['h', '155', '3899', '9577', 'F', 'U', 'a', '6441', 'o', 'a', 'u', 'y', 'R', '2365', '5325', 'M', 'L', '2765', '865', '4575']