Let $L$ be the line of intersection of the planes $x + y = 0$ and $y + z = 0$.\\
(a) Write the vector equation of $L$, i.e., find $(a, b, c)$ and $(p, q, r)$ such that
$$L = \{(a, b, c) + \lambda(p, q, r) \mid \lambda \text{ is a real number.}\}$$
(b) Find the equation of a plane obtained by rotating $x + y = 0$ about $L$ by $45^\circ$.