Confidence Intervals · Challenge problem

In a random sample of $600$ voters choosing between two candidates (everyone picks one), $330$ choose Smith and $270$ choose Jones. Smith's lead is $\hat p_S - \hat p_J$. Find the LOWER end of the $95\%$ confidence interval for Smith's true lead $p_S - p_J$, using $z^* = 1.96$. Round to four decimal places.