If a young man drives his vehicle 25 km/hr he has to spend Rs. 2 per km on petrol. If he drives it at faster speed of 40 km/hr, the petrol cost increases to Rs. 5 per km. He has Rs. 100 to spend on petrol and travel within one hour. The maximum distance he travels is :

20 km 100 km 30 km 50 km

30 km