Free advice at social affairs?

A doctor and a lawyer were attending a cocktail party when the doctor was approached by a man who asked advice on how to handle his ulcer. The doctor mumbled some medical advice, then turned to the lawyer and remarked, “I never know how to handle the situation when I’m asked for medical advice during a social function. Is it acceptable to send a bill for such advice?” The lawyer replied that it was certainly acceptable to do so. The next day, the doctor sent the ulcer-stricken man a bill. The lawyer also sent one to the doctor.