Sam needs to make a long-distance call from apay phone. with his prepaid phone card, he will be charged $1.00 to connect and $0.50 per minute. if he places a collect call with the operator he will be charged $3.00 to connect and $0.25 per minute. in how many minutes will the phone card and the operator-assisted call cost the same?
a.5 minutes
b. 51/3 min.
c. 8 min.
d. 16 min.

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?