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.
['r', '1153', '279', 'H', 'L', 'V', 's', '5543', 'm', '2241', 's', '939', 'o', 'N', 'V', 'I', '7031', 'Q', 'w']