The mass of the earth is about 6 × 10/\−2 times the mass of Neptune. The mass of the earth is about 6 × 10/\24 kg. What is the mass of Neptune? Give your answer in scientific notation.
6 × 1026 kg
1 × 10/\28 kg
1 × 10/\26 kg
6 × 10/\28 kg

Aspacecraft can attain a stable orbit 300 kilometers above earth if it reaches a velocity of 7.7 kilometers per second. the formula for a rocket's maximum velocity v in kilometers per second is vequalsminus0.0098tplusc ln upper r, where t is the firing time in seconds, c is the velocity of the exhaust in kilometers per second, 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 2.1 km/s, and a firing time of 15 s. can the spacecraft achieve a stable orbit 300 km above earth?