Consider a reaction whose rate law is first-order in X and first-order in Y. A pseudo-first-order kinetic run is performed with initial concentrations of 0.500 M X and 0.0100 M Y. The observed pseudo-first-order rate constant for this reaction was measured to be 0.419 1/s. Based on this information, which compound (X or Y) has a concentration that changes with time over the kinetic run? Using the data above, calculate the experimental rate constant for the reaction with correct units [M/s, 1/s, or 1/(Ms)). Report your value to three significant figures