Compare an earthquake with a Richter scale magnitude of 5.5 to one with a magnitude of 7.5.
A. 2 times stronger
B. 1000 times stronger
C. 100 times stronger
D. 20 times stronger

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