A $U$-shaped tube is partially filled with an incompressible liquid of density $1.2 \mathrm{g} {\mathrm{cm}}^{-3}.$ Oil which does not mix with the liquid is next poured into the left side of the $U$-tube until the liquid rises by, $15 \mathrm{cm}$ on the right side of $U$-tube. If the density of the oil is $0.9 \mathrm{g} {\mathrm{cm}}^{-3},$ the oil level will stand higher than the liquid level of the right side of $U$-tube by

• A

  $15 \mathrm{cm}$
• Correct answer
  B

  $10 \mathrm{cm}$
• C

  $12 \mathrm{cm}$
• D

  $9 \mathrm{cm}$

Hence, the correct answer is option: 'B'.