13.1 A two-stage, solid-propellant sounding rocket has the following properties: PROBLEMS 733 First stage: m0 249.5 kg mf 170.1 kg m_ e 10:61 kg=s Isp 235 s Second stage: m0 113.4 kg mf 58.97 kg m_ e 4:053 kg=s Isp 235 s The delay time between burnout of first stage and ignition of second stage is 3 s. As a preliminary estimate, neglect drag and the variation of earth's gravity with altitude to calculate the maximum height reached by the second stage after burnout.