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.
['5967', 'c', 'k', '2243', 'v', 'Z', '5379', '7705', 'n', '2151', 'U', '4805', '6179', 'd', 'A', 'u', '8419', '9799', 'k']