Chemical Kinetics

Rate of reaction, $\mathrm{A}+\mathrm{B} \rightarrow$ product, is $7.2 \times 10^{-2} \mathrm{moldm}^{-3} \mathrm{~s}^{-1}$ at $[\mathrm{A}]=0.4 \mathrm{~mol} \mathrm{dm}^{-3}$ and $[B]=0.1 \mathrm{~mol} \mathrm{dm}^{-3}$. The reaction is first order in A and second order in B. Calculate rate constant.