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.
['N', 'B', 'K', '8423', '6043', 's', '7283', 'n', '6377', 'n', 'd', '933', 'v', '2289', '5587', 'x', 'K', 's', 'v', 'B']