Ben took a train and traveled 80 km. Then, he boarded a bus that increased the rate of his trip by 4

Ben took a train and traveled 80 km. Then, he boarded a bus that increased the rate of his trip by 4

Ben took a train and traveled 80 km. Then, he boarded a bus that increased the rate of his trip by 4 kph and traveled 120 km. His entire trip took him 20 hours. What was the rate of his travel on a train?​