The castle has a mass of 500 grams and a volume of 250 mL. How much water does it displace? 500 grams or 250 mL ?

250 mL

Explanation:

If the density is more than that of water (in this case it is) it will sink to the bottom of the container holding water (if it fits).

That being the case, the amount of water displaced = the volume of the castle.

250 mL

here we know that ball will drop down by total distance 3.2 m

so here we know that

now using kinematics

now in the same time it will cover horizontal distance of 0.75 m

so speed of the ball will be

see earlier