ANSWER
b. 36π units²
EXPLANAION
As stated in the question, the formula to find the surface area of a sphere of radius r is,
[tex]SA=4\pi r^2[/tex]
In this case, the radius is 3 units,
[tex]SA=4\cdot\pi\cdot3^2=\pi\cdot4\cdot9=36\pi\text{ }units^2[/tex]
Hence, the surface area of this sphere is 36π square units.
