By The Associated Press___ Tiny Chevrolet Sonic helps Detroit shake off rust DETROIT (AP) â¿¿ When the word reached the Orion Assembly Plant, it spread along the serpentine assembly line like news of a death or natural disaster: General Motors, the biggest automaker in the world, had filed for bankruptcy protection. On that grim day in 2009, Chevrolet and Pontiac sedans kept rolling down the line. And 1,700 worried workers stayed at their stations even as GM announced it would close the plant in a desperate bid to survive. There was something else that the workers didn't know: They were witnessing the opening act of one of the greatest recovery stories in American business. Nearly four years later, Chevrolets are still moving down the assembly line under the plant's 82-acre roof. Lang and his co-workers now build the Sonic, the best-selling subcompact car in the nation. It's a vehicle no one thought could be made profitably in the U.S., by a company that few people thought would last. But GM has not only survived, it has earned $16 billion in profits in the past three years. And the industry is on track to make this year its best year since 2007. ___ US economy adds 155,000 jobs; rate remains 7.8 pct. WASHINGTON (AP) â¿¿ U.S. employers added 155,000 jobs in December, a steady gain that shows hiring held up during the tense negotiations to resolve the fiscal cliff. The solid job growth wasn't enough to reduce the unemployment rate, which remained 7.8 percent last month, the Labor Department said Friday. The rate for November was revised up from an initially reported 7.7 percent. Each January, the government updates the monthly unemployment rates for the previous five years. The rates for most months don't change. The government said hiring was stronger in November than it first estimated. November's job increases were revised up 15,000 to 161,000. October's increase was nearly unchanged at 137,000.