Use v=-0.0098 t+c ln R , where v is the velocity of the rocket, t is the firing time, c is the velocity of the exhaust, and R is the ratio of the mass of the rocket filled with fuel to the mass of the rocket without fuel. Find the velocity of a spacecraft whose booster rocket has a mass ratio of 20 , an exhaust velocity of 2.7km/s, and a firing time of 30 s . Can the spacecraft achieve a stable orbit 300km above Earth?