The reaction $X + Y \to Z$ is first order with respect to X and second order with respect to Y. Initial rate of formation of Z = R mol dm$^{-3}$ sec$^{-1}$ when $[X]$ and $[Y]$ are 0.40 mol dm$^{-3}$ and 0.30 mol dm$^{-3}$ respectively. If $[X]$ is halved and $[Y]$ is doubled, the value of the initial rate would become