A group of high school seniors were surveyed on their interests. Of those surveyed, 16 students said they enjoy reading, and 14 said they enjoyed writing. What additional information would you need to know in order to determine how many students said they enjoy both reading and writing?
a) The number of students who enjoy reading only.
b) The number of students who enjoy writing only.
c) The number of students who don't enjoy neither reading nor writing.
d) The number of students said they enjoy either reading or writing.