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.
['1989', '8323', '881', '3521', 'I', 'Y', '9779', '3795', 'x', 'o', 'B', '3811', 'L', 'D', 'v', 's', 'V', '1557', 'Z', 'd']