Exercise 6. Before handing back the papers to his students, a teacher made a few statistical calculations based on the series of their marks:  Mean: 11  Median: 12  1 st quartile: 9  3 rd quartile: 13  Minimum mark: 4  Maximum score: 15 We also know that there are 25 students in the class. Answer true or false to the following statements 1. Half the students have a mark below 11. 2. At least one student scored 12. 3. At least one student scored 13. 4. Half the grades in the class are between 9 and 13. 5. The median is the 12th mark in the series of marks arranged in ascending order.