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.
['j', 'A', '6479', '8725', '9125', '2441', '7221', 'R', '9759', '5853', 'n', 'G', 'j', 'o', 'o', 'R', '5985', 's']