The speed of a boat in still water is 20 km/hr and the rate of current is 5 km/hr. The distance travelled downstream in 24 minutes is:  Choose the correct choice from the following.
A) 9
B) 5
C) 7
D) 6
E) 10

Rationale: "explanation : speed downstream = ( 20 + 5 ) kmph = 25 kmph distance travelled = ( 25 * ( 24 / 60 ) ) km = 10 km . answer : e"
Answer: E