The driver of an ambulance sees a school bus 40 m ahead of him after 20 seconds, the school bus is 60 meter behind. If the speed of the ambulance is 30 km/h, what is the speed of the school bus?

• ক 12 kmph ✅ সঠিক উত্তর
• খ 22 kmph
• গ 15 kmph
• ঘ 10 kmph