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.
['v', 'k', '4029', 'a', 'P', 'v', 't', '5703', '4913', 'i', '8301', '7885', 'A', '1091', 'v', '1423', '5961', 'W']