Area = pi*r^2
Circumference = pi*d
d is the diameter, which is equal to twice the radius, as such C = 2pi*r is also an acceptable formula for the circumference of a circle.
I assume that you've already got the answers since Mr. Fantastic gave you the formulas, so if you want to make sure you've done it correctly:
A = pi*r^2
A = (3.14)*(8.6)^2
A = (3.14)*(73.96)
A = 232.2344 cm^2
C = 2pi*r
C = 2(3.14)(8.6)
C = 6.28(8.6)
C = 54.008 cm
Any more Questions don't hesitate to ask