Obstacle avoiding and line following autonomous robot 2 wd

See I want use three ultrasonic sensors in my obstacle avoiding robot with track following
Can u give me a idea on programming it with tree of them if any body can send the invoice

Hi there. What do you want the robot to do when it detects something? How are the sensors arranged?

So what to do if there's an obstacle on the line it has to follow? Either you're going to run into the obstacle, or you lose the line you're supposed to be following!

send the invoice

What, without fixing a price?