The sum of the digits in the unit's place of all the 4-digit numbers formed by using the numbers $3,4,5$ and $6$, without repetition is: (1) 18 (2) 36 (3) 108 (4) 432
The sum of the digits in the unit's place of all the 4-digit numbers formed by using the numbers $3,4,5$ and $6$, without repetition is:\\
(1) 18\\
(2) 36\\
(3) 108\\
(4) 432