We need to buy a lot, so we would go to wholesale supermarket to buy our groceries. The closest wholesale place is BJ's Wholesale Club, which is 12 miles away. Ms. Lam drives you and your classmates to BJ's Wholesale Club. On the way back, due to traffics, she drives 6 miles per hour slower, resulting in the return trip taking 4 minutes longer. How fast did she drive on the way to the BJ's Wholesale Club? (be careful, change the time from minutes to hours)

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?