Two concentric current loops lie in the same plane. The smaller loop has a radius of $2\mathrm{.}3$ cmcm and a current of $12$ AA$.$ The bigger loop has a current of $20$ AA $.$ The magnetic field at the center of the loops is found to be zero.

Part A

What is the radius of the bigger loop?

Express your answer with the appropriate units.

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RR $=$

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