<image> At the beginning, a motor vehicle has 42 liters of fuel in the tank, and after driving for some hours, it refuels at a gas station. The remaining fuel amount in the tank Q (in liters) as a function of the driving time t (in hours) is shown in the figure. Answer the questions:

(1) After how many hours of driving does the vehicle refuel?
(2) ___ liters of fuel were added during refueling.
(3) Given that the gas station is 240 km away from the destination and the vehicle's speed is 40 km/h, is the fuel in the tank enough to reach the destination? Explain the reason.