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.
['j', '1149', 't', '6389', 'n', '9745', '8701', '6277', '8901', 'd', '6769', '3511', '4647', '541', '5285', '3523', 'Y', '3683', '9473', 'B']