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.
['y', '2449', '2455', 'c', 'k', '1331', '6695', '6195', 'V', 'Y', '9897', 'Y', '4155', '9057', '4829', 'a', 'D', 'Z', 'F']