Let X = {x1, x2, x3, x4} and let b : X × X → [0, ∞) be symmetric with b(x1, x2) = b(x2, x3) = b(x3, x4) = b(x4, x1) = 1 and 0 otherwise. Let c = 0. Let f(x1) = 0 = f(x2), f(x3) = 1, and f(x4) = 0. Let α = 1. Find u which satisfies (Lb,c + α)u = f. Is u unique? Why or why not? What happens when you solve (Lb,c + α)u = 0 instead?