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.
['8325', '8289', '4227', 'u', 'Y', 'x', '2281', 's', 'k', 'R', '2877', '7115', '7065', '7927', 'A', '9287', 'M', '2375', '6667', 'f']