A car uses 8.4 litres of gas for every 100 km it is driven. A mechanic is able to modify the car's engine at a cost of \$400 so that it will only use 6.3 litres of gas per 100 km. The owner determines the minimum distance that she would have to drive to recover the cost of the modifications. If gas costs \$0.80 per litre, this distance, in kilometres, is between
(A) 10000 and 14000 (B) 14000 and 18000 (C) 18000 and 22000 (D) 22000 and 26000 (E) 26000 and 30000
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Source: CEMC, University of Waterloo,
licensed CC-BY-NC-4.0.
Statement reproduced verbatim; metadata (topic, difficulty) added by this project. Solutions are the publisher's, linked not copied.