The reaction $$X + Y \rightarrow Z$$ is first order with respect to X and second order with respect to Y. The initial rate of formation of Z is R $$\text{mol dm}^{-3} \text{s}^{-1}$$ 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

A

4R

B

$$\frac{R}{4}$$

C

R

D

2R