Answer:
4361.5 km/h
Step-by-step explanation:
v = Velocity of space vehicle = 4300 km/h
= Velocity of exhaust
= Velocity of module
Relative velocity

4m = Mass of rocket
m = Mass of module
3m = Mass of rocket without module
In this system linear momentum is conserved

The speed of the command module relative to Earth just after the separation is 4361.5 km/h