Car a gets 25 miles per gallon and costs $13,000. car b is a hybrid that gets 45 miles per gallon, but costs $25,000. assume you drive 15,000 miles per year and that gas will cost $4 per gallon for the foreseeable future. how many years will it take for car b's better fuel economy to outweigh its higher initial cost?

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?