Four engineers are travelling in an old Land-Rover, when it suddenly breaks down. The engineers are a mechanical engineer, a chemical engineer, an electrical engineer and a computer engineer.
They all have different opinions on the cause of the trouble.
Mechanical engineer: "Sounds to me like the pistons have seized. We'll have to strip the engine down and rebuild it."
Chemical engineer: "It sounded to me like contaminated fuel. I think we should clear out the fuel system."
Electrical engineer: "I thought it might be a grounding problem. We ought to check the plug wiring."
Computer engineer: "Er, perhaps if we get out and then go back in again that'll cure the problem."