Identify the correct statement regarding the order of reaction from the following.

In the reaction,$P + Q \longrightarrow R + S$,the time taken for $75 \%$ reaction of $P$ is twice the time taken for $50 \%$ reaction of $P$. The concentration of $Q$ varies with reaction time as shown in the figure. The overall order of the reaction is

Rate of reaction is $r_1 = k[A]^a[B]^b$. If the concentration of $A$ is doubled and $B$ is halved,the new rate is $r_2$. What is the value of $\frac{r_2}{r_1}$?

For a certain chemical reaction $X \rightarrow Y$,the rate of formation of the product is plotted against time as shown in the figure. The number of correct statement$(s)$ from the following is $.......$.
$A$. Overall order of this reaction is one
$B$. Order of this reaction cannot be determined
$C$. In region-$I$ and $III$,the reaction is of first and zero order respectively
$D$. In region-$II$,the reaction is of first order
$E$. In region-$II$,the order of reaction is in the range of $0.1$ to $0.9$.

For the reaction,$PCl_5 \longrightarrow PCl_3 + Cl_2$,the rate and rate constant are $1.02 \times 10^{-4} \ mol \ L^{-1} \ s^{-1}$ and $3.4 \times 10^{-5} \ s^{-1}$ respectively at a given instant. The molar concentration of $PCl_5$ at that instant is

For the reaction, $A + B \rightarrow P$, the rate law is $\text{rate} = k[A][B]^2$. The rate of reaction is $0.25 \text{ Ms}^{-1}$ when $[A] = 1 \text{ M}$ and $[B] = 0.2 \text{ M}$ at $25^\circ \text{C}$. Calculate the rate constant $k$ of the reaction at the same temperature.