An expected rip-off? A “psychic” runs the following ad in a magazine:

Expecting a baby? Renowned psychic will tell you the sex of the unborn child from any photograph of the mother. Cost, $20. Money-back guarantee.

This may be a profitable con game. Suppose that the psychic simply replies

“boy” to all inquiries. In the worst case, everyone who has a girl will ask for her money back. Find the expected value of the psychic’s profit by filling in the table below.

Sex of child Probability The psychic’s profit Boy 0.51 Girl 0.49