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.
['5293', '5303', 'm', 'I', 'B', 'S', '1795', '9523', '5805', '4155', '1879', '9777', 'D', 'o', 'B', '2921', '663', 'k']