Question

when studying the reaction A+B--C+D, a student mixed together known concentrations A and B, the timed the appearance of D, a colored compound. the first trial contained 0.05 mol A and 0.1 mol B. the measured time was 60 sec. the second trial contained 0.1 mol A and 0.1 mol B, and the reaction took 29 sec. what is the order of the reaction with respect to A? explain.