A Comet Fragment of Mass 1

Multiple Choice

A comet fragment of mass 1.96 × 10¹³ kg is moving at 6.50 × 10⁴ m/s when it crashes into Callisto, a moon of Jupiter. The mass of Callisto is 1.08 × 10²³ kg. The collision is completely inelastic.
-Assuming for this calculation that Callisto's initial momentum is zero kg . m/s, what is the recoil speed of Callisto immediately after the collision?

A) 3.34 × 10^-18 m/s
B) 1.27 × 10^-14 m/s
C) 3.58 × 10^-12 m/s
D) 6.13 × 10^-7 m/s
E) 1.18 × 10^-5 m/s