Radius of convergence question

[theBEAST]

Homework Statement

Suppose that the following series converges when x = -4 and diverges when x = 6.
∑{n=0 -> ∞} c_n • x^n

What is the interval of convergence?

The Attempt at a Solution

I think it is [-5,5) but my friend reckons that it is [-5,6). I don't think [-5,6) is correct because this interval would tell us that 5 is a point of convergence but we don't know that... Am I right?

 

[LCKurtz]

You don't have enough information. All you know for sure is you have a radius of convergence at least 4 and not more than 6.