TASK DEFINITION: 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.
PROBLEM: ['1391', '1719', '8547', 'x', 'a', 'j', '6395', 't', '3421', '6607', 'M', '1645', 'H', 'x', 't']

SOLUTION: 29725

PROBLEM: ['8109', '5635', 'u', 'M', '1009']

SOLUTION: 14753

PROBLEM: ['S', '71', 'Q', 'R', 'c', '3719', 'T', 'M', '7061', 'b', 'd', 'n', '4217']

SOLUTION:
15068