Two balls of different masses are dropped from a building, and they hit the ground at the same time. How does the force of gravity, exerted on each ball, depend on its mass?
A
It is independent of the ball’s mass.
B
It is directly proportional to the ball’s mass.
C
It is inversely proportional to the ball’s mass.
D
It is directly proportional to the ball’s mass squared.

An electric power distributor charges residential customers $0.10 per kilowatt-hour (kwh). the company advertises that "green power" is available in 150 kwh blocks for an additional $4 per month. (green power is generated from solar, wind power, and methane sources.) if a certain customer uses an average of 391 kwh per month and commits to one monthly 150 kwh block of green power, what is her annual power bill