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.
['H', '1383', 'I', 'E', 'S', '975', '8129', 't', 'z', '7915', 'R', '41', 'o', '4603', 'z', '8795', '4103', 'E', '5441']