Answer:
Step-by-step explanation:
Given that the half life of 3H is 12.3 years.
The amount of substance left of a radioactive substance with half life of

after t years is given by

Therefore, the number of years it will take for 18% of the original tritinum to remain is given by

Therefore, the number of <span>years that the time could be read at night is 30.4 years.</span>
Your answer is d. hope this helps
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