3. Every hour on the hour, a train leaves Smallville and travels along a straight track to Bigtown, a trip that takes 4 hours and 15 minutes. Every hour on the hour, a train also leaves Bigtown and travels to Smallville along a parallel track, making a trip that also takes 4 hours and 15 minutes. Charlie rides the 7 p.m. train that leaves Smallville and counts the trains that pass by from Bigtown on the parallel track during his trip. How many trains go by?