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.
['T', 'L', '6597', '2807', '1445', '6181', 'M', 'u', 'A', 'd', '571', 'U', '3931', 'W', '4547', '6733', 'u', '4463', 'q']