A certain mayor has proposed a fee of five dollars per day on private vehicles entering the city, claiming that the fee will alleviate the city’s traffic congestion. The mayor reasons that, since the fee will exceed the cost of round-trip bus fare from many nearby points, many people will switch from using their cars to using the bus.
Which of the following statements, if true, provides the best evidence that the mayor’s reasoning is flawed?
(A) Projected increases in the price of gasoline will increase the cost of taking a private vehicle into the city.
(B) The cost of parking fees already makes it considerably more expensive for most people to take a private vehicle into the city than to take a bus.
(C) Most of the people currently riding the bus do not own private vehicles.
(D) Many commuters opposing the mayor’s plan have indicated that they would rather endure traffic congestion than pay a five-dollar-per day fee.
(E) During the average workday, private vehicles owned and operated by people living within the city account for twenty percent of the city’s traffic congestion

what's wrong with E.. if the private vehicles are only 20 percent then the plan will not work in reducing the traffic congestion.
please elaborate..