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', '7977', '7267', 'y', '8189', '8285', 'F', 't', 'S', 'Y', '4013', '9795', 'A', '3351', 'R', 'N', 'h', 'H', '6843', 'w']