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.
['5299', '659', '4187', 'a', '8291', 'J', '7091', 'l', 'i', 'J', 'k', 't', 'M', 'k', 'A', '4099', '9149', '7205', 'm']