While John is traveling along a straight interstate highway. he notices that the mile marker reads $258 km$. John travels until he reaches the $145 km$ marker the retraces his path to the $168 km$ marker. What is John’s resultant displacement and how far has he traveled from the $258 km$s marker?

The first-order reaction a→2b+c has rate constant 0.538 s−1. if the initial concentration of a is 0.867 mol l−1, what is the half-life of the reaction in seconds? remember to use correct significant figures in your answer (round your answer to the nearest hundredth). do not include units in your response.