Penobscot County commissioners have chosen a Bangor architectural and engineering firm to design a new jail for the county. But in the process of choosing WBRC Architects and Engineers, the county has again changed the cost and scope of its plans for a replacement of the current aging and overcrowded jail on Hammond Street. County commissioners on Tuesday voted unanimously to pay WBRC $267,420 to design what is now expected to be a 250-bed, stand-alone jail estimated to cost $44.8 million — less than two months after commissioners sought bids from firms to design a 300-bed, $65 million jail.