A Satellite, Initially at Rest in Deep Space, Separates into Two

Multiple Choice

A satellite, initially at rest in deep space, separates into two pieces, which move away from each other. One piece has a rest mass of $190 \mathrm {~kg}$ and moves away with a speed $0.280 \mathrm { c }$ , and the second piece moves in the opposite direction with a speed $0.600 \mathrm { c }$ . What is the rest mass of the second piece?

A) $73.9 \mathrm {~kg}$
B) $88.7 \mathrm {~kg}$
C) $79.6 \mathrm {~kg}$
D) $52.7 \mathrm {~kg}$
E) $68.8 \mathrm {~kg}$