How does a catalyst appear in a chemical equation

Determine the rate law, including the values of the orders and rate law constant, for the following reaction using the experimental data provided. a + b yields products trial [a] [b] rate 1 0.30 m 0.25 m 1.2 × 10-2 m/min 2 0.30 m 0.50 m 4.8 × 10-2 m/min 3 0.60 m 0.50 m 9.6 × 10-2 m/min