Final $3$: Assume that there are $12$ letters and $4$ numbers and one month. I will create two passwords both contain four characters to login the system. To login a system you need two passwords at the same time $($one is for the first layer if the password is correct then you enter the second layer password$-$if you find the correct passwords you can login the system$-$ when you select a character in the first layer you cannot select the same character in the second layer$).$ I create a four characters' password containing four letters for the first layer and for the second layer I create another password that contains two letters and two numbers. What is the probability that you guess the passwords for the next month? $(5$ Demicals$)$