Chemical Kinetics Questions

The energies of activation for forward and reverse reactions for $A_2+B_2\rightleftharpoons 2AB$ are $180{\text{kJ mol}}^{-1}$ and $200{\text{kJ mol}}^{-1}$ respectively. The presence of a catalyst lowers the activation energy of both (forward and reverse) reactions by $100{\text{kJ mol}}^{-1}$. The enthalpy change of the reaction ($A_2+B_2\to 2AB$) in the presence of catalyst will be (in ${\text{kJ mol}}^{-1}$):

Consider the reaction, $2A+B\to \text{Products}$. When concentration of $B$ alone was doubled, the half-life did not change. When the concentration of $A$ alone was doubled, the rate increased by two times. The unit of rate constant for this reaction is: