The rate constant of reaction 2A+B→C is 2.57×10−5 L mole−1sec⁡−1 after 10 sec, 2.65×10−5 L mole−1sec⁡−1 after 20 sec and 2.55×10−5 L mole−1sec⁡−1 after 30 sec. The order of the reaction is: