The speed of a boat in still water in 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is:
Choose the correct choice from the following answers:
A) 1.2 km B) 2.4 km C) 3.2 km D) 3.6 km E) 4.6 km

Rationale: "speed downstream = ( 15 + 3 ) kmph = 18 kmph . distance travelled = 18 x 12 / 60 km = 3.6 km . answer : d"
Answer: D