Your roommate just bought a Nike+ Sportwatch for $160. She would have been willing to pay $250

Question:

Your roommate just bought a Nike+ Sportwatch for $160. She would have been willing to pay $250 for a device that could improve her morning runs by measuring the speed, distance, and duration of the runs, and calculating the calories she burns. How much consumer surplus does your roommate enjoy from the Nike+ Sportwatch?