Let A be the set of students at your school and B the set of books in the school library. Let R₁ and R₂ be the relations consisting of all ordered pairs (a, b), where student a is required to read book b in a course, and where student a has read book b, respectively. Describe the ordered pairs in each of these relations.

a) R₁ ∪ R₂
b) R₁ ∩ R₂
c) R₁ ⊕ R₂
d) R₁ − R₂
e) R₂ − R₁