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.
['q', '4741', '3943', 'm', '7203', '5031', 'H', '4639', 'r', 'j', 'Y', '9055', 'M', '7555', '4833', '655', '2121', 'l', 's', 'X']