 (The function of uniform substitution \(σ\) is defined as follows. Let \(B\) be a formula in \(\mathcal{L}\), let \(p_1,\ldots, p_n\) be all the propositional variables occurring in \(B\), and let \(σ(p_1) = A_1,\ldots , σ(p_n) = A_n\) for some formulas \(A_1 ,\ldots ,A_n\). Then \(σ(B)\) is the formula that results from B by substituting simultaneously \(A_1\),…, \(A_n\) for all occurrences of \(p_1,\ldots, p_n\), respectively.)