7. A student took a multiple-choice test with five choices per answer. Assume that the student knew the correct answer to 70% of the questions and guessed on the rest of them. If an answer is returned marked correct, what is the probability that the student really knew the answer, given each of the following conditions? a. On the questions that the student did not know, he or she guessed completely at random. b. On the questions the student did not know, he or she was able to narrow each answer down to three choices. c. Explain how the results of Parts a and b are related