17. Quasar Q₁ is moving away from us at a speed of 0.8 C. Quasar Q₂ is moving away from us in the opposite direction at a speed of 0.5 C. The speed of Q₂ as measured by an observer on Q₁ is: ("C" is the speed of light)
(A) 0.3 C
(B) 0.65 C
(C) 0.93 C
(D) 1.0 C
(E) 1.3 C.

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