Distance between two stations A and B is 778km. A train covers the journey from A to B at 84 km per hour and returns back to A with a uniform speed of 56 km per hour. Find the average speed of train during the whole journey.

• ক 57 km/hr
• খ 67.2 km/hr ✅ সঠিক উত্তর
• গ 30.5 km/hr
• ঘ 60 km/hr