Practice Calculating Rocket Efficiency

Goddard, the engineer responsible for developing the first ever liquid-fuel rockets, (go to our engineering lesson to learn more!: (url)), started off with a simple solid fuel design, which used gunpowder to create thrust. Given that gunpowder has a q value of 5*10^6, and the exit velocity of exhuast was around 600 m/s (again, accurate to Goddards rockets), calculate the theoretical efficiency of his solid fuel design, assuming that the mass of the exhuast ejected is the same as the mass of the starting fuel.