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.
['745', 'p', 'h', 'r', 'B', '6023', '213', 'U', 'U', '9779', 'X', 'e', 'B', '5025', 'x', '6243', 'r', 'P', '3335']