Answer: sphere
Step-by-step explanation:
For cone,
Radius = 9 in.
height = 12 in.
Volume = [tex]\dfrac{1}{3}\pi r^2h[/tex]
Then, Volume = [tex]\dfrac{1}{3}(3.14)(9)^2(12)=1017.36\ \text{cubic inches}[/tex]
For cylinder,
Radius = 9 in.
height = 12 in.
Volume = [tex]\pi r^2h[/tex]
Then, volume = [tex](3.14)(9)^2(12)=3052.08\text{ cubic inches}[/tex]
For sphere,
Radius = 9 in.
Volume = [tex]\dfrac{4}{3}\pi r^3[/tex]
Then, volume = [tex]\dfrac{4}{3}(3.14)(9)^3=3052.08\text{ cubic inches}[/tex]
For best buy, we require highest volume but lowest cost.
Thus, Volume of cone < Volume of cylinder and volume of sphere.
Volume of cylinder = volume of sphere.
But the cost of the sphere < cost of cylinder as $28<$30.
So, the sphere would be the best buy as it has the greatest volume but low cost.