Rick Santorum suspends his presidential campaign, clearing the way for Mitt Romney to claim the Republican nomination. President Obama continues to press his case for the proposed tax reform that would require millionaires to pay 30 percent of their income in federal taxes. A new book aims to dymystify the national debt. Best Buy CEO Brian Dunn resigned this morning. Health reporter Gregory Warner explains why medical billing codes are so significant. And we look into why only 35 percent of hybrid owners choose to buy another hybrid when it's time to trade in.