Riddle: Dr. Susan Schwerdtfeger bumped into an old college friend. "Hello," she said. "I haven't seen or heard from you since graduation in 1983. What's happened to you?"
"Well," said the friend. I got married in 1989 to someone you wouldn't know, and this is my son." "hello" said Susan to the boy. "What's your name?" It's the same as my father's, said the boy. "Ah" said Susan, so your name must be Peter." How did Susan know?