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.
['l', '2499', '9297', '1315', 'M', 'q', 'i', 'i', '4331', '2551', '5133', 'b', 'a', '8807', 't', 'H', 'q', '5149']