One interval is given in interval notation, another in set-builder notation. Match the equivalent intervals to the right answer.
1. (-∞, 7)
2. (7, ∞)
3. (-∞, ∞)
4. [7, ∞)
a. {x l -∞ < x <7}
b. {x l 7 < x < ∞}
c. {x l x ∈ ℝ}
d. {x l 7 ≤ x < ∞}
1. a
2. b
3. c
4. d