Taxi drivers, whose income is based on the fares they receive, usually decide when to finish work each day by setting a daily income target; they stop when they reach that target. This means that they typically work fewer hours on a busy day than on a slow day. The facts described above provide the strongest evidence against which one of the following? ["The number of hours per day that a person is willing to work depends on that person's financial needs.", 'People who are paid based on their production work more efficiently than those who are paid a fixed hourly wage.', 'People work longer when their effective hourly wage is high than when it is low.', 'Workers will accept a lower hourly wage in exchange for the freedom to set their own schedules.']