2022 JPJC P2 Q6

A computer is used to generate codes consisting of four letters followed by two digits. Each of the four letters generated is equally likely to be any of the twenty-six letters of the alphabet “A – Z”. Each of the two digits generated is equally likely to be any of the ten digits “\(0-9\)”.

Find the probability that a randomly chosen code has

1. four different letters and two different digits[2]
2. two different consonants and two different vowels, where the consonants and vowels alternate,[3]
3. two letters the same, two letters different and two digits the same.[3]