An online food delivery company charges \(Rs.\) 50 as a fixed delivery cost and \(Rs.\) 20 per \(km\) for the distance from the restaurant.
1. The constant base fare is \(Rs.\) and the rate of change is \(Rs.\) .
2. The linear expression for the given situation is .
3. If the delivery person receives a total cost of \(Rs.\)250 , then the total distance he drove is \(kms\).