A man starts walking at 3 pm. he walks at a speed of 4 km/hr on level ground and at a speed of 3 km/hr on uphill, 6 km/hr downhill and then 4 km/hr on level ground to reach home at 9 pm. What is the distance covered on one way?

• A. 12 km
• B. 23 km
• C. 45 km
• D. 65 km