WASHINGTON (AP) - In the aftermath of storms that knocked out power to millions, sweltering residents and elected officials are demanding to know why it's taking so long to restring power lines and why they're not more resilient in the first place. The answer, it turns out, is complicated: Above-ground lines are vulnerable to lashing winds and falling trees, but relocating them underground incurs huge costs - as much as $15 million per mile of buried line - and that gets passed onto consumers.