None .. theres no solution
A line of symmetry is when you can put a line through a shape and you can fold it and it is identical on both sides, and rotational is when you can rotate it and at some point it is in the same spot as it was before, so yes, you are right. the octogon.
55 cubic units because
- each cube is equal to 1 cubic unit
- the total volume is 60 cubic units
- 5 cubes are already inside
B c and d if I am correct