What is the magnitude of the magnetic field inside the toroid

[mr_coffee]

A toroid having a square cross section, 5.00 cm on a side, and an inner radius of 16.0 cm has 600 turns and carries a current of 0.700 A. (It is made up of a square solenoid bent into a doughnut shape.)

(a) What is the magnitude of the magnetic field inside the toroid at the inner radius?
5.25e-4 T
(b) What is the magnitude of the magnetic field inside the toroid at the outer radius?
? T

I keep missing part B. I tried:
B = PERMIVITY*n*I
where n = N/(2PI*R);
N is the number of turns:
R is the radius of the toroid. PERMITIVITY = 4PIE-7;
So i plugged in
n = 600/(2PI*.05)
B = 4PIE-7*.700*n which was wrong! any ideas?

 

[haruspex]

square cross section, 5.00 cm on a side, and an inner radius of 16.0 cm

So what is the outer radius?