Which situation is modeled by the equation below?
 100 + (-100) = 0
 A. winning $100 in a contest, then paying a $100 electric bill
 B. winning $100 in a contest, then donating half of it to a charity
 C. paying $100 for a video game system, then paying $100 more for video games
 D. paying $100 for a video game system, then selling it to someone else for $200