A reactor is filled with a mixture of reactants A and B, which undergo an exothermic reaction to form product C. The initial concentration of A and B are 2 mol/L and 3 mol/L respectively, and the rate of reaction is given by the equation: r = kC_A^2C_B

Where r is the rate of reaction (mol/L/s), k is the reaction rate constant (L/(mol*s)), and C_A and C_B are the concentrations of A and B (mol/L).

If the reaction rate constant k is equal to 0.1 L/(mol*s), calculate the rate of reaction (r) at time t = 0, 20, 40, 60, and 80 seconds.