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. A rocket has a mass ratio of 24 and an exhaust velocity of 2.5km/s . Determine the minimum firing time for a stable orbit 300km above Earth.