6. A leaky valve on the water meter overcharges the residents for one gallon of water every 3 1/3 months.
The overcharged amount w varies directly with
time t. Find the equation that models this direct
variation. How many months it will take for the
residents to be overcharged for 9 gallons of water?

A. w = 3/10 t; 2 7/10 months

B. w= 3/10 t; 30 months

C. w= 10/3 t; 30 months

D. w= 10/3 t; 2 7/10 months

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?