Resolution of optical binaries

[radiosource]

Imagine a double star with components separated by 10 astronomical units (10 AU). How far away can such a system be while remaining resolved with a 300 mm telescope? Show workings and give your final answer in either light years or parsecs. (Ignore atmospheric effects).

Thanks.

[ideasrule]

Since this is obviously a homework problem, it should go into the "Homework and Coursework" section. You're also expected to show your attempts at the problem, as well as any relevant equations.

I'll start you off: what limits the angular resolution of a telescope? (In reality the answer is almost always "atmospheric effects", but the question wants you to ignore that.)