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.
['B', 'C', 'W', 'N', '909', '647', 't', '3705', 'C', '203', '5631', 'g', 'e', 'T', 'Z', 'W', 'G', 'E', '6101']