Rate Laws Questions

For reaction $aA\to xP$, when $[A]=2.2\text{mM}$, the rate was found to be $2.4{\text{mM s}}^{-1}$. On reducing concentration of $A$ to half, the rate changes to $0.6{\text{mM s}}^{-1}$. The order of reaction with respect to $A$ is: