A single reservoir supplies the petrol to the whole city, while the reservoir is fed by a single pipeline filling the reservoir with the stream of uniform volume. When the reservoir is full and if 40,000 liters of petrol is used daily, the suply fails in 90 days.If 32,000 liters of petrol is used daily, it fails in 60 days. How much petrol can be used daily with out the supply ever failing?
Answers:
A) 64000 liters B) 56000 liters C) 78000 liters D) 60000 liters E) none of these

Rationale: explanation : let x liter be the per day filling and v litr be the capacity of the reservoir , then 90 x + v = 40000 × 90 - - - - - ( 1 ) 60 x + v = 32000 × 60 - - - - - - ( 2 ) solving eq . ( 1 ) and ( 2 ) , we get x = 56000 hence , 56000 liters per day can be used without the failure of supply . answer : b
Answer: B