A problem on a multiple-choice VirtuaGATE quiz at Techtud is answered correctly with probability 0.9 if a student is prepared. An unprepared student guesses between 4 possible answers, so the probability of choosing the right answer is 1/4. Seventy-five percent of students prepare for the quiz.

If Mr. Sumit gives a correct answer to this problem, what is the chance that he did not prepare for the quiz?