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.
['3583', '8305', '5765', '8591', '9365', 'w', 'G', 'Y', 'G', 'H', '9951', '9287', '7985', '5401', '1017', 'm', 'x', '4633', 'j', '4257']