A pipe transporting an unknown fluid $($with a density of $1000$ kg$/$m$3)$ goes through a transition that changes the diameter from $2$ meters $($D$1)$ to $1$ meter $($D$2)$ as shown. Before the transition the velocity is $1$m$/$s$.$

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What is the velocity $($in m$/$s$)$ after the transition?

What is the difference in pressure $($in Pa$)$ between Point #$1$ and Point #$2($P$1-$ P$2)?$