Identify the product $Z$ in the following sequence of reactions.

$\mathrm{Phenol}\stackrel{\mathrm{NaOH}}{\to }\mathrm{X}\underset{4-7\mathrm{atm},410\mathrm{K}}{\overset{{\mathrm{CO}}_2}{\to }}\mathrm{Y}\stackrel{{\mathrm{H}}_3{\mathrm{O}}^{+}}{\to }\mathrm{Z}$

 

Phenoxide ion generated by treating phenol with sodium hydroxide it under goes to electrophilic substitution  with  carbon dioxide  a weak electrophile orthohydroxy benzoic acid (Salicylic acid) is formed as main reaction product. This is also called as Kolbe’s reaction.