Four people walk along the circumference of a park. They walk at 20 m/min, 10 m/min, 25 m/min and 30 m/min respectively. The circumference of the park is 1200m. After how long will they be at the starting point together if they have started all at th

• A. 240 min
• B. 480 min
• C. 160 min
• D. 120 min