A wall is made of two layers of thickness $1\  cm$ and $4\  cm$ and thermal conductivities $K$ and $3K$ respectively. If temperature difference for the wall is $50\ ^oC$ then temperature difference for the thin layer will be

  • A

    $\frac{120}{7}\ ^oC$

  • B

    $\frac{150}{7}\ ^oC$

  • C

    $\frac{180}{7}\ ^oC$

  • D

    None

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