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.
['Q', 'S', '9305', '869', '1489', '2665', 'w', 'J', '7695', '643', 'D', '6097', '5941', 'T', 'R', '9137', 't', 'v', 'Q', 'f']