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.
['s', 'V', '2541', 'Z', '303', 'R', '3633', '3903', 'X', 'M', '5727', '2921', '169', '7463', '8501', 'c', '9951', 'K', 'K', '5109']