The stock is up 7.5% to about $18 after G Asset Management disclosed that it has offered to pay $22 a share for 51% of the retail book chain — or $5 a share for 51% of the Nook tablet and e-reader business. The investment firm says that its offers are contingent on its ability to obtain financing, due diligence and — in the bid for the whole company — access to its credit facility and cash on the balance sheet. Barnes & Noble confirms that it has received the proposal, but declined to comment. G Asset Management says that in November it made an offer that valued B&N at $20 a share. “In that proposal, GAM suggested that the company should immediately separate the unprofitable Nook segment from the college and retail segment and recommended commencing a rights offering for the Nook segment to existing shareholders,” it says. The firm says it’s still “extremely confident that if the Nook segment is separated from the profitable retail and college business, substantial shareholder value would be created.” B&N is scheduled to talk with analysts on Wednesday about its financial performance at the end of 2013.