Consider a 3-stage rocket with the following design. First stage propellant mass 7100kg and structure 900kg. Second stage propellant mass 5400kg and structure mass 600 kg. Third stage: propellant mass 3000kg and structure 500 kg. The payload mass is 60 kg. The specific impulses for all the stages are 275s. In a test, the second stage failed to ignite after the first stage was burned out. So the NASA operator decided to discard the second stage and directly ignite the third stage. + Questions: What was the final velocity of this rocket?