According to the above given formula, If pipe A  and B fills a tank in x and y hours respectively, but a third pipe C empties the full tank in z hours then the net portion filled in 1 hour when all of them are opened together is $\frac{\mathrm{xyz}}{\mathrm{yz}+\mathrm{xz}-\mathrm{xy}}$ hours.

According to the question x+y+z=120

So,

 $$\begin{gathered} 120=\frac{180\times 140\times \mathrm{z}}{(180\times 140)+(140\times \mathrm{z})+(\mathrm{z}\times 180)} \\ 120=\frac{25200\mathrm{z}}{25200+140\mathrm{z}+180\mathrm{z}} \\ 120=\frac{25200\mathrm{z}}{25200+320\mathrm{z}} \end{gathered}$$

Upon cross multiplication,

$$\begin{gathered} 120\left(25200+320\mathrm{z}\right)=25200\mathrm{z} \\ 3024000+38400\mathrm{z}=25200\mathrm{z} \\ 3024000=25200\mathrm{z}-38400\mathrm{z} \\ 3024000=13200\mathrm{z} \\ \mathrm{z}=\frac{3024000}{13200} \\ \mathrm{z}=229.09 \mathrm{minutes} \end{gathered}$$

Therefore, the tank will be emptied in 229.09 minutes.

Hence option B is correct.