A prudent young man.....

A police officer, at nearly midnight, saw a couple in a car at Lovers' Lane with the interior light brightly glowing.
He carefully approached the car to get a closer look. He saw a young man behind the wheel reading a computer magazine.
He then noticed a young woman in the rear seat, filing her fingernails.
Puzzled by this surprising situation, the officer walked to the car and gently rapped on the driver's window.
The young man lowered his window. "Uh, yes, officer?"
The cop asked, "What are you doing?"
The young man said, "Well, officer, I'm reading a magazine."
Pointing towards the young woman in the back seat the officer asked, "And her, what is she doing?"
The young man shrugged, "Sir, I believe she's filing her fingernails."
Now, the cop was totally confused. A young couple, alone, in a car, at night in Lover's Lane and nothing is happening!
He asked, "What's your age, young man ?"
The young man said, "I'm 22, sir."
The cop asked, "And her, what's her age?"
The young man looked at his watch and replied,"She'll be 18 in 11 minutes.