An instructor for a class that meets on mondays, wednesdays, and fridays announces on friday that there will be a pop quiz next week. the students have to decide what day to study. in terms of performance, it is best to study the evening before the pop quiz. thus, on each of the evenings before the possible day of the quiz, students decide whether or not to study. (note that a student may end up studying more than one evening if at first she thinks the test is on, say, wednesday and thus studies tuesday evening, but it turns out the quiz is on friday in which case she’ll study thursday evening as well.) the instructor, who is an unpleasant sort, wants to minimize students’ grades and thus would most like to have it on a day when the students did not study the evening before. everything else the same, he prefers to give it earlier in the week. find the spne.