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.
['G', '4893', 'l', 'K', 'M', 'b', '1967', '9365', '7275', 'p', '5753', 'm', 'Y', '6345', '3639', 'o', '5449', 'J', '685', '1909']