An intercity cab service has a lumpsum fixed charges of Rs. 800 upto certain kilometres.
Beyond that the charges are per kilometres.
When two passengers separately travelled total 450 km, they were charged Rs. 2600 and Rs. 2000 respectively.
If a single passenger had travelled all 450 km, he would have been charged Rs. 5000.
How many kms are allowed for first Rs. 800?