Question $2(2\mathrm{.}5$ points$)$

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For the Power System's Slack $($Infinite$)$ bus type, which of the Real power, Reactive power and Voltage $($P$,$ Q$,$ and V $)$ variables of that bus are unspecified $($i$.$e$.,$ must be solved$)$ for power flow analysis?

$V$ and $P$ are unspecified

$V$ and $Q$ are unspecified

$P$ and $Q$ are unspecified