A code consists of 4 digits. The digits are chosen from \{1, 2, 3, 4, 5, 6\}. Suppose that repetitions are allowed, find the probability that a code chosen at random
(i) has the digits arranged in a decreasing order from the left to the right and no two consecutive numbers are the same,
[2]
(ii) ends with an even digit,
[1]
(iii) contains the digit 2 exactly once or ends with an even digit, but not both.
[4]