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.
['4363', 'Y', 'r', '3027', '7635', 'V', '5855', 'l', '7505', '4187', '8131', 'P', 'M', '5169', '577', '9635', 'm', '4083', 'L']