-----Description-----  
The problem asks you to construct a new list by adding an extra number to the end of an existing list of numbers. The focus is on understanding what the final list should look like when a given number is included as the last element.

-----Input-----  
The input consists of:  
• a: An array of integers.  
• b: An integer to be appended to the array.

-----Output-----  
The output is an array of integers which represents the original array with the element b added at the end. That is, the output array’s list representation equals a.toList concatenated with [b].

-----Note-----  
There are no special preconditions; the method is expected to work correctly for any array of integers and any integer b.