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.
['4407', '5215', 'N', '4343', '1483', '7945', 't', '6197', '4381', '7467', 'l', '3743', 'A', '3405', '2057', '9899', '2429', '4533', 'g', 's']