Problems and Exercises 10 through 15 are based on the relations shown in Figure 6-12. Th...

Problems and Exercises 10 through 15 are based on the relations shown in Figure 6-12. The database tracks an adult literacy program. Tutors complete a certification class offered by the agency. Students complete an assessment interview that results in a report for the tutor and a recorded Read score. When matched with a student, a tutor meets with the student for one to four hours per week. Some students work with the same tutor for years, some for less than a month. Other students change tutors if their learning style does not match the tutor’s tutoring style. Many tutors are retired and are available to tutor only part of the year. Tutor status is recorded as Active, Temp Stop, or Dropped.

What is the average length of time a student stayed (or has stayed) in the program?