Question

Can someone help me draw the logic gate circuit of the problem below please. And Help me understand it

Rods of varying length (± 10%) travel one at a time in the direction of their longest axis on a conveyor belt. A mechanical arm pushes rods that are within specification (± 5%) off the belt to one side. A second arm pushes rods that are too long to the other side. Rods that are too short remain on the belt. Use three light barriers (light source + photocell) as sensors, and design the combinational circuits that activate the two arms.