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.
['f', 'a', '9237', '4765', 'p', 'W', '5387', 'H', 'u', 'N', '3237', '6815', '8065', 'z', 'Q', '2943', '6283', 'B', 'm']