Let \( f: \mathbb{R} \times \mathbb{R} \to \mathbb{R} \) be defined as:
\[ f(x, y) = \begin{cases} \frac{x}{\sqrt{x^2 + y^2}} & \text{if } (x, y) \neq (0, 0) \\ 1 & \text{if } (x, y) = (0, 0) \end{cases} \] Then, which of the following statements is true?
Five friends A, B, C, D, and E are sitting in a row facing north, but not necessarily in the same order:
B is to the immediate left of C
E is not at any of the ends
D is to the right of E but not next to C
A is at one of the ends
Who is sitting in the middle?