Two objects, each of weight w, hang vertically by spring scales as shown in the figure. the pulleys and the strings attached to the objects have negligible weight, and there is no appreciable friction in the pulleys. the reading in each scale is

a: more than 2w.
b: less than w.
c: more than w, but not quite twice as much.
d: w.
e: 2w.

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