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.

Example input: ['238', 'h', '92', 'U', '2799']
Example output: 3129
Example explanation: Here, the numbers in the input list are '238', '92' and '2799', hence their sum (238+92+2799) is 3129.
Q: ['s', 'Q', 'f', 'r', 'h', '521', 'D']
A:
521