Calculate Bohr Radius of Hydrogen Atom (n=600)

[1v1Dota2RightMeow]

I'm doing a homework problem where it asks to calculate the diameter of a hydrogen atom with n=600. I used the equation $$r=\frac{n^2a_0}{Z}$$ where $$a_0=0.529e^{-10}m$$.

Solving for r yields:

$$r=\frac{(600^2)(0.529e^{-10}m)}{1}=1.90e^{-5}m$$

Multiplying by 2 to get the diameter yields:

$$d=2r=2(1.90e^{-5}m)=3.80e^{-5}m$$

However, the answer given says that d=1.90e^-5m, but how can this be? I know that the equation above yields the radius of an electron's orbit, but why would they claim that it's the diameter? Did I miss something?

 

[mfb]

I guess they mixed diameter and radius in the problem statement. Or did they use helium? I don't see other options to get a factor of 2.