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.
['D', 'B', 'e', '4047', '5325', 'Y', '1677', '3363', 'E', '6867', 'P', 'Y', 'g', '363', '7259', 'R', '2839', 'A']