Car producer energy efficiency

A car producer aims at making an existing model more efficient. Because of the improvements the car should now use 6.3L of gasoline instead of 7L of gasoline pre 100km. ;

Assuming average customer drives 20000km per year, pay-back-period of 3 years and gasoline prices is $1.30. ;

The adaptions in the first produced new model will cost $1700. How many more efficient cars must the producer produce in order to stay below the additional price ($546)? Use a progress ratio of 0.9 for the additional costs.