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.
['5677', '7837', '5263', '4467', '4395', '7203', '963', '5855', 'a', '6765', 'N', '613', 'V', 'R', 'M', 'E', '8157', '4333', 'a', 'd']