Question 4
Picture 1 shows a castle built from identical cubes. Picture 2 shows the same castle from above. How many cubes were used?

As intended by the drawing, each visible tower is supported by a solid column of cubes; the two lower square-ring layers have no hidden gaps.

As intended by the drawing, each visible tower is supported by a solid column of cubes; the two lower square-ring layers have no hidden gaps.