 We want to show that \(S = 1\) is an actual cause of \(W = 1\). Conditions AC(1) and AC(2) are clearly satisfied. For condition AC(3), we choose \(\bX = \{S\}\) and \(\bZ = \{B\}\). Since \(B = 0\) in Preemption, we want to fix \(B = 0\) while varying S. We can see easily that \({S = 0} \amp {B = 0} \boxright {W = 0}\): replacing the two equations for B and S with \(B = 0\) and \(S = 0\), the solution yields \(W = 0\). In words, this counterfactual says that if neither Billy nor Suzy had thrown their rock, the window would not have shattered. Thus condition AC(3a) is satisfied. AC(3b) is satisfied trivially, since \(\bX = \{S\}\) is a singleton set.