A man was polishing a light-bulb before inserting it into the socket, when there was a big flash and a genie appeared before him.

`I am the genie of the light-bulb,' he said.

`I will answer any three questions for you - but only three. Do you have three questions you would like to ask?'

`Who? Me?' said the man.

`Yes, you,' said the genie.

`Now, what is your third question?'