Let Bi = {x ∈ ℝ|0 ≤ x ≤ i} for each integer i = 1, 2, 3, 4. (a) Find B1 ∪ B2 ∪ B3 ∪ B4. (Enter your answer using interval notation.) (b) Find B1 ∩ B2 ∩ B3 ∩ B4. (Enter your answer using interval notation.) (c) Are B1, B2, B3, and B4 mutually disjoint? Explain. Yes, because no two of the sets B1, B2, B3, B4 have any elements in common. Yes, because the union of the sets B1, B2, B3, B4 is empty. Yes, because the intersection of the sets B1, B2, B3, B4 is empty. No, because no two of the sets B1, B2, B3, B4 are disjoint. No, because the sets B1, B2, B3, B4 are disjoint.