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.
['N', '8831', 'K', '415', 'w', '6771', '5129', 'X', 'j', 'T', 'v', 'q', 'Z', 'J', '2815', 'f', '3247', '7187']