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.
['3351', '6445', 'Y', '8455', 'V', 'z', 'a', 'V', 'S', '8551', '4101', 'q', '8743', '5999', '7155', '3825', '2241', '9957']