A set of words {qs, tq, ut, pqr, srt] is to be transmitted using a binary code

Question:

A set of words {qs, tq, ut, pqr, srt] is to be transmitted using a binary code for each letter, (a) Show that it is possible to select one letter from each word as a system of distinct representatives for these words, (b) If a letter is selected at random from each of the five words, what is the probability that the selection is a system of distinct representatives for the words?