Suppose you are navigating a spacecraft far from other objects. The mass of the spacecraft is $2\mathrm{.}0\backslash$times $104$ kg $($about $20$ tons$).$ The rocket engines are shut off, and you're coasting along with a constant velocity of $<0,32,0>$ km$/$s$.$ As you pass the location $<8,4,0>$ km you briefly fire side thruster rockets, so that your spacecraft experiences a net force of $<4\backslash$times $105,0,0>$ N for $24\mathrm{.}0$ s$.$ The ejected gases have a mass that is small compared to the mass of the spacecraft. You then continue coasting with the rocket engines turned off. Where are you an hour later? $($Think about what approximations or simplifying assumptions you made in your analysis. Also think about the choice of system: what are the surroundings that exert external forces on your system?$)$ what is rf$=?$