The reaction A + B --> P is found to be first order in both A and B. The reaction was carried out in a solution that was initially 0.080 mmol dm^-3 in A and 0.060 mmol dm^-3 in B. After 1.0h the concentration of B had fallen to 0.030 mmol dm^-3. (i) Calculate the rate constant. (ii) What are the half-lives of the reactants?