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.
['M', 'R', 'r', '6661', '517', '3539', '5665', 'd', 'r', '3965', 'j', '4735', '9325', '9297', '1661', '5751', '9013', '1483']