A boat moves upstream at the rate of 1 km in 25 minutes and down stream 1 km in 12 minutes. Then the speed of the current is :
Choose the correct choice:  A) 1 kmph  B) 2 kmph  C) 3 kmph  D) 1.3 kmph  E) 3.5 kmph

Rationale: "rate upstream = ( 1 / 25 * 60 ) = 2.4 kmph rate dowm stream = 1 / 12 * 60 = 5 kmph rate of the current = ½ ( 5 - 2.4 ) = 1.3 kmph answer : d"
Answer: D