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.
['2663', 'l', '7863', 'Y', '6965', '5979', '8895', '9501', '1321', 'K', '7921', 'q', '8701', 'K', '1839', 'U', 'G', '7867', 'd']