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', '235', '7119', 'P', '825', '479', 'q', 'k', 'R', 'L', '1697', 'F', 'L', '1091', 'z', 'L', 'H', 'M', 'R']