The tenth-grade class is planning a homecoming dance. They want to hire a band. Band A: The band charges 500 to play for the night. Band B: The band charges 275 and 1.50 for every ticket sold. Let n represent the number of tickets sold and c represent the total cost of hiring a band. Which systems of equations model this situation?

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?