Linear programming problem

Linear programming problem
If a person drives his car at rate 25 km/h he has to spend rupees 2 per km on per liter
If he drives at faster speed of 40 km /h the petrol cost increases by 5 per km.He has rupees 100 to spend on petrol and wishes to find what max distance he can travel one hour is. Express this in the form of linear programming problem.

This is quite a stupid question, as it's well known that it takes more petrol to travel at a faster speed. So to travel the furthest distance he should travel at the slowest possible speed (25 km/h).