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.
['k', '1373', 'E', '4543', 'E', 'k', 'U', 'P', 'b', '8083', '5631', '4395', '4265', '9963', 'F', '8893', '639', 'p']