A Satellite with a Rest Mass of 200 Kg and a Speed

Multiple Choice

A satellite with a rest mass of 200 kg and a speed of 0.800c and a second satellite with a rest mass of 100 kg and a speed of 0.600c are traveling toward each other in deep space. The satellites collide
And somehow manage to stick together. What is the rest mass of the combined object after the
Collision?

A) 389 kg
B) 300 kg
C) 587 kg
D) 416 kg
E) 457 kg