which of the following represents a function?

(5, 2), (6, 2), (-5, -2), (-6, -2)

(-3, 4), (-3, 4), (-3, -4), (-3, -4)

(4, 1), (4, 2), (4, 3), (4, 4)

Acar started driving from city a to city b, distance between which is 620 miles, at a rate of 60 mph. two hours later a truck left city b and started moving towards city a at a rate of 40 mph. how many hours after the truck's departure will the two meet?