An athlete runs along the perimeter of an equilateral triangle of side 20 km. He runs along the first side at 20 km/hr, along the second at 25 km/hr, and along the third at 30 km/hr. What is his average speed?(INFOTECH COMPANY)

• A. 22.72 km/hr
• B. 27.42 km/hr
• C. 24.32 km/hr
• D. 25.30 km/hr