Well, I'm assuming you haven't had your question answered yet in these 58 minutes. I'm not 100% sure but I would think that you would do the reverse of the equation to find the area of a circle to find the radius of the pizza cutter. So you would find the radius using the equation A=
r 
to figure out the RADIUS. THEN, you would plug in the radius into the equation C= to figure out the circumference. Next, you would multiply the circumference by 4. This would give you the diameter of the pizza. Finally, you would plug in the diameter of the pizza into this equation: A= to find the area of the pizza. I am pretty sure this would work and there's probably an easier way that I don't know about. Assuming you get this in time, good luck! :)