The mixed table-and-graph visual gives A: -7->11, -6->-6, -5->-5, 6->-3, 7->-2 and B: (-8, 1), (-1, -6), (4, 6), (7, -8), (12, -5). The composition A(B(x)) can fail when the B-output is not an input for A. Which listed x makes it undefined?