[tex] \large \mathbb{SOLUTION}[/tex]
[tex] \bold{Top \: diameter \: = \: 6 \: inches}[/tex]
[tex] \bold{Bottom \: diameter \: = \: 15 \: inches}[/tex]
[tex] \underline \bold{Diameter \: of \: middle \: shelf:}[/tex]
Therefore, the answer in 10.5 inches.
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