Aldehyde And Ketone

What is the major product $Z$ in the given reaction sequence?

$$ \left(\mathrm{CH}_3\right)_2 \mathrm{C}=\mathrm{O} \xrightarrow[\text { (ii) } 2 \mathrm{H}_2 \mathrm{O}^{+}]{(\mathrm{i}) \mathrm{C}_2 \mathrm{H}_5 \mathrm{MgBr}} \xrightarrow[\Delta]{\substack{\text { (i) } \mathrm{OOCl}_2 \\ \text { (ii) } \mathrm{CH}_3 \mathrm{ONa}}} Y \xrightarrow[\text { Peroxide }]{\mathrm{HBr}} Z $$