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.
['7539', '4603', '7737', 'a', '1279', '8281', '5901', 'v', 'q', 'd', 'k', '4199', 'K', 'Z', '9247', '8151', '2917', 'R', '2643', 'd']