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.
['3135', 'T', '9377', 'x', 'l', '3547', '8889', '8833', 'B', '7261', 'b', '765', 'j', '3799', 'Z', '491', 'd', '1677']