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.
['K', 't', '3705', 'T', '8525', 'n', '2077', 'F', '6107', 'X', '895', 'o', 'H', '4507', 'A', '8495', '6459', 'T']