A stage rocket accelerates

A two stage rocket accelerates at 10m/s for 3 seconds and 4,3m/s for further 7 seconds.The initial mass was 200 Tonnes.After the first stage the mass drops to 80 tonnes.The thrust for the first stage is 4000000 N and for the second stage is 2860000 N.Calculate the velocity at the end of stage 1 and 2.Also calculate the change in momentum for the first and second stages of the rocket's momentum.

Question From: Benias Maguvaza - Feb 8th 2010