#### Explanation:

Let the cruise ship's profit by represented by $P$ and the amount of rooms booked be represented by $r .$ We can represent this by the equation

$P = 125 r$, as we're told that each room $r$ costs $125. So, if there are $250$rooms booked, the we simply plug in $r = 250$into the above equation for the profit: $P = 125 \left(250\right) = 31250$The cruise ship makes $31,250.