Radius:
From the figure we notice that the radius is 3 units.
Diameter:
The diameter is twice the radiues, hence the diameter is 6 units.
Circumference:
The circumference is given by:

where D is the diamteter, therefore the circumference is:

Area:
The area is given by:

where r is the radius, plugging the values we have:

therefore the area is:
