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.
['1545', 'M', '385', '5977', 'b', 'i', 'k', '769', '1117', '4523', 'D', '5063', '619', '4767', '8303', '8769', '659', '9839']