Help! I have a half-dead kitten.?

So my dad recently found a little 4 or 5 week old kitten wandering around the farm. He's not from any of our cats. Anyway, he put him in a box and then took him over to our house. The problem is that the cat is half-dead. He barely moves and has mucus all around his nose, and one eye is all gunked up and shut. What should I do? What can I feed him? I have lamb milk replacer and normal milk - should I warm some up and feed him with a dropper? He's really weak - please help ASAP