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.
['3719', 'n', 'T', '2127', '7703', 'c', 'v', 'D', '1699', 'u', '9143', '1661', '2069', '5083', 'w', 'b', 'F', '3505', '4333']