What do they mean by convenient radius. How much measure should we take?

Dear Student,

Please find below the solution to the asked query:
$$\begin{gathered} \mathrm{Convenient} \mathrm{radius} \mathrm{is} \mathrm{like} \mathrm{you} \mathrm{can} \mathrm{take} \mathrm{any} \mathrm{length} \mathrm{of} \mathrm{radius} \mathrm{that} \mathrm{you} \mathrm{are} \mathrm{comfortable} \mathrm{with} \\ \mathrm{You} \mathrm{can} \mathrm{take} 1 \mathrm{m} \mathrm{or} 2\mathrm{m} \mathrm{or} 3\mathrm{m} \mathrm{or} \mathrm{else} \end{gathered}$$

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