There was stand-off in the Persian Gulf today involving Iranian gunboats and a British warship escorting a tanker. The Iranians attempted to block the passage of the tanker, but backed off when confronted by the Royal Navy frigate. The Gulf is the source of 20% of the world’s oil and the tensions with Iran could endanger that. Host Marco Werman speaks with Ellen Wald, an energy consultant and author of “Saudi, Inc.”