To determine the age of rock #4, you would use Uranium-238 rather than Carbon-14. The reasoning is as follows:
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Uranium-238 is typically used for dating geological samples that are millions to billions of years old. It is suitable for dating igneous and metamorphic rocks since it has a very long half-life (about 4.5 billion years).
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Carbon-14 is only effective for dating relatively younger organic material, up to about 50,000 years, because it has a much shorter half-life (about 5,730 years).
Given the context that rock #4 is estimated to be in the age range of 700-750 million years, Carbon-14 would not be appropriate for dating this rock since it falls far outside the range of what Carbon-14 can effectively date.
Therefore, the correct response would be:
700-750 Million Years; Uranium-238; because rock is non-living.