There are 300 students in a twelfth grade high school class. 120 of these students have at least one sister and
100 have at least one brother. Out of the students that have at least one brother, there are 40 who have at least
one sister and one brother.
Let A be the event that a randomly selected student in the class has a sister and B be the event that the
student has a brother. Based on this information, answer the following questions.