Identify Z in the following sequence

$$\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{I} \xrightarrow{\mathrm{KCN}} X \xrightarrow{\mathrm{H}_3 \mathrm{O}^{+} / \mathrm{H}_2 \mathrm{O}} \mathrm{Y} \xrightarrow[\Delta]{\mathrm{H}_3 \mathrm{O}^{+} / \mathrm{H}_2 \mathrm{O}} Z$$

The reaction given below is an example of which of the following?

$$2 \mathrm{CH}_3 \mathrm{Br}+2 \mathrm{Na} \xrightarrow{\text { dry ether }} \mathrm{C}_2 \mathrm{H}_6+2 \mathrm{NaBr}$$