' $x$ ' is the product which is obtained from benzene by reacting it with carbon monoxide and hydrogen chloride in the presence of cuprous chloride. ' $y$ ' is the major product obtained from the benzene by reacting it with ethanoyl chloride in the presence of anhydrous $\mathrm{AlCl}_3$. Product (major) obtained by heating x and y in the presence of alkali is z . Total number of $\pi(p i)$ electrons in z is $\_\_\_\_$