Ten juniors from high school were given the opportunity to visit a nearby university

Chapter 14, Problem 11

(choose chapter or problem)

Ten juniors from high school were given the opportunity to visit a nearby university with the possibility of attending that university in the future. The day of their visit, however, happened to be one of the days when final exams were given in the high school. Some of the students missed exams in history (H), English (E), government (G), biology (B), mathematics (M) and French (F). The exams the ten students missed are given below. Alvin: H, E Brenda: E, F Charles: M, F Dina: M, B Edwin: E, G Fan: H, F Ghia: M, H Howard: H, E, G Ida: B, G John: F, B The next day after the students returned to high school, they were required to take make-up exams for the exams they missed. What is the smallest number of time periods in which all exams can be given if two different exams cannot be given during the same period if some student must take both exams?