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.
['6131', '1007', 'g', 'M', 'h', 'd', '6729', '1831', '2563', '2197', 'l', 'v', 'n', '4445', 'V', 'K', 'N', 'f', 'w', '8305']