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.
['o', '8089', '2159', '943', '1255', 'w', 'Y', '3723', 'n', '7767', '2209', 'F', 'c', 'J', '5259', '4427', 'n', 'U']