Autility company charges $0.14 per kilowatt -hour for energy a customer uses. they give a credit of $0.035 for every kilowatt-hour of electricity a customer with a solar panel generates that they dont use themselves. how many kilowatt-hours did they use?

Atourist boat is used for sightseeing in a nearby river. the boat travels 2.4 miles downstream and in the same amount of time, it travels 1.8 miles upstream. if the boat travels at an average speed of 21 miles per hour in the still water, find the current of the river.