Late night vehicle check

A State Trooper was patrolling late at night off the main highway. At nearly midnight, he sees a couple in a car, in lovers' lane, with the interior light brightly glowing. He carefully approaches the car to get a closer look. Then he sees a young man behind the wheel, reading a computer magazine.

He immediately notices a young woman in the rear seat, filing her fingernails.

Puzzled by this surprising situation, the trooper walks to the car and gently raps on the driver's window. The young man lowers his window. 'Yes, Officer'?

The trooper asks: 'What are you doing?'

The young man says: 'Well, Officer, I'm reading a magazine.'

Pointing towards the young woman in the back seat the trooper says: 'And, her, what is she doing?'

The young man shrugs: 'Sir, I believe she's filing her fingernails.'

Now, the trooper is totally confused. A young couple, alone, in a car, at night in a lover's lane and nothing obscene is happening!

The trooper asks: 'What's your age, young man?'

The young man says: 'I'm 21, sir.'

The trooper points to the back seat and asks: 'How old is she?'

The young man looks at his watch, smiles, and replies:'Well, sir, she'll be 18 in 11 minutes.'