To calculate the rate constant k for the reaction A + B C, we can use the Arrhenius equation:k = Ae^-Ea/RT where:k = rate constantA = pre-exponential factor also known as the frequency factor Ea = activation energy 50 kJ/mol R = gas constant 8.314 J/molK T = temperature 300 K However, we do not have the value of the pre-exponential factor A in the given information. Therefore, we cannot calculate the exact value of the rate constant k for this reaction.As for predicting the order of the reaction based on the proposed mechanism, we need more information about the reaction mechanism, such as the elementary steps and their molecularity. The overall order of the reaction is determined by adding the molecularity of each elementary step in the rate-determining step slowest step of the mechanism. Without this information, we cannot predict the order of the reaction.