Give Me Your Wallet (And Your Watch) (слэш)

It was pushing midnight when Peter sent a text to his friend Ned asking for help with a chemistry problem. I know I'm doing something wrong but I can't figure it out, he wrote.
He received a text with a picture of the solution. The elegant script should have been the first clue; the fact that it was on the back of a napkin the second. But he was tired, and failed to notice such details.
You misplaced your decimal when converting degrees to Kelvin, came the reply. Rookie mistake.
Gee, thanks, Peter replied with a roll of his eyes. Anything you need help with?
Yeah, who the fuck am I talking to, exactly?
(AKA the wrong number AU)