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
Answer Choices
A. 10\:000 and 14\:000
B. 14\:000 and 18\:000
C. 18\:000 and 22\:000
D. 22\:000 and 26\:000
E. 26\:000 and 30\:000