Let S be the sample space of all 3 × 3 matrices with entries from the set {0, 1}. Let the events E₁ and E₂ be given by E₁ = {A ∈ S : det A = 0} and E₂ = {A ∈ S : sum of entries of A is 7}. If a matrix is chosen at random from S, then the conditional probability P(E₁|E₂) equals _____.