Help me with this please

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.

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A15 ohm resistor and a 25 ohm resistor are connected in a series to a 60 volt battery. what is the power used by each device