The reaction X + Y Z is first order with respect to X and second order with respect to Y . The initial rate of formation of Z = R mol ⁻ dm ^3 sec ⁻¹ when [ X ]₀ and [ Y ]₀ are 0.40 ~mol dm ⁻³ and 0 . mol dm ⁻³ respectively. If [X]₀ is halved and [Y]₀ is doubled, the value of the initial rate would become