A Laser Beam Takes 24 Ms to Travel from a Rocket

Multiple Choice

A laser beam takes 24 ms to travel from a rocket to the reflective surface of a planet and back to the rocket. How far is the rocket from this planet's surface? $\left( c = 3.0 \times 10 ^ { 8 } \mathrm {~m} / \mathrm { s } \right)$

A) $1200 \mathrm {~km}$
B) $3600 \mathrm {~km}$
C) $4800 \mathrm {~km}$
D) $1800 \mathrm {~km}$
E) $2400 \mathrm {~km}$