A bus covered a distance of 250 km, partly at an average speed of 40 kmph and partly at 60 kmph. If the total time taken is 5.5 hours, then the distance covered at 40 kmph is  Choose the correct choice from the following answers:
A) 130 km
B) 160 km
C) 100 km
D) 140 km
E) none of these

Rationale: "let the partial distance covered at 40 kmph be x let the another partial distance covered at 60 kmph be ( 250 - x ) thus , x / 40 - ( 250 - x ) / 60 = 5.5 or , x / 40 + ( 250 - x ) / 60 = 5.5 or , ( 3 x + 500 - 2 x ) / / 120 = 5.5 or 500 + x = 660 x = 160 answer : b"
Answer: B