It’s a no-win scenario: You rush to the emergency room, pay a co-pay, then get hit with a surprise bill — hospital was in network, but the doctor wasn’t. One study found that mismatch happens in as many as one in five ER visits, and it’s a source of bubbling rage over health care costs. Today, we look into how it happens. Plus: what you need to know about the trade truce with China and Taylor Swift’s fight over the rights to her music.