Appeared in: 2026 (2 sets)
If $$\vec{a} + \vec{b}$ \cdot $\vec{a} - \vec{b}$ = 198$ and $|\vec{a}| = 10 |\vec{b}|$, then :
(A) $|\vec{a}| = \sqrt{2}$
(B) $|\vec{b}| = \sqrt{2}$
(C) $|\vec{b}| = 10\sqrt{2}$
(D) $|\vec{a}| = \frac{10}{\sqrt{2}}$