For $\mathrm{A}+\mathrm{B}\to \mathrm{P}$ the initial rates are: $[\mathrm{A}]=0.10$, $[\mathrm{B}]=0.04\mathrm{M}$, rate $=0.0160$; $[\mathrm{A}]=0.20$, $[\mathrm{B}]=0.04\mathrm{M}$, rate $=0.0320$; $[\mathrm{A}]=0.10$, $[\mathrm{B}]=0.16\mathrm{M}$, rate $=0.0320\mathrm{M}{\mathrm{s}}^{-1}$. Select the correct statements.

1. AThe order with respect to $\mathrm{B}$ is $1/2$.
2. BThe overall order is $3/2$.
3. C$k=8.0{\mathrm{M}}^{-1/2}{\mathrm{s}}^{-1}$.
4. DHalving $[\mathrm{A}]$ and quadrupling $[\mathrm{B}]$ together leaves the rate unchanged.