A stairwell in a certain office building is always congested at 12:00 p. m. and 1:00 p. m. The congestion is so bad that people have been complaining to the building's owner. Which of the following methods would be the most efficient way of reducing congestion?
a. Charge everyone who uses the stairwell when it is congested the same fee. People who value the use of the stairs the most will be the ones who use the stairwell at peak times. b. Assign each person in the building a time when they are allowed to use the stairwell. c. Hold a lottery to determine who wins the right to use the stairwell at peak times. d. Encourage people to voluntarily keep off the stairwell during peak times.