Four middle school American history teachers have given their students a three-item essay quiz test on a Friday and plan to score the tests over the weekend. Each of the three items is worth 10 points, for a total of 30 points on the quiz. Because she has a large number of students, and to avoid fatigue, Jan Williamson scores a few items late Friday afternoon, scores several more on Saturday, and finishes the scoring process on Sunday afternoon. She scores the third item for all the students first, the second item second, and the first item last to avoid knowing whose paper she is scoring. Luis Alvarez has his students write their names on the last page of the test, so he doesn't know their identity as he scores the items, and he writes a model answer for each question that his uses as a guide in scoring his students' papers. He then scores the first item for all the students, turns to the second item and does the same, and repeats the process for the third item. Helen Walker is a conscientious and professional teacher who has the best interests of the students at heart. She wants to