The consumption of diesel per hour of a bus varies directly as square of its speed. When the bus is travelling at 50 kmph its consumption is 1 litre per hour. if each litre costs $30 and other expenses per hous is $ 20, then what would be the minimum expenditure required to cover a distance of 400 Km? Select:
A) 300  B) 400  C) 250  D) 350  E) 450

Rationale: "50 kmph consumption is 1 lt / hr so 400 km will take 8 hrs and the consumption is 8 lt for entire distance . 1 lt costs $ 30 so 8 lt costs $ 240 extra expenses for 1 hr - $ 20 8 hrs - $ 160 total expense - $ 240 + $ 160 = $ 400 answer : b"
Answer: B