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.
['8515', 'l', '4409', '7359', '1957', '9137', '9841', '3439', '7759', 'r', 'p', 'a', '9957', '6163', 'n', 'G', 'G', 'B', 'B', '9479']