Assign structures for the following.

A hydrocarbon $\left(\mathrm{Z}\right)$ has molecular formula ${\mathrm{C}}_8{\mathrm{H}}_{10}$. It does not decolourise bromine water and is oxidised to benzoic acid on heating with ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$. It can also have three other isomers $\mathrm{A}$, $\mathrm{B}$ and $\mathrm{C}$. Write the structures of $\mathrm{Z}$ , $\mathrm{A}, \mathrm{B}$ and $\mathrm{C}$.