Shares of AMC Networks plunged more than 35% Monday as the company said it plans put up for sale $125 million-worth of convertible senior notes due in 2029 in a private offering, plus additional notes for up to $18.75 million. The public company controlled by the Dolan family and run by Kristin Dolan expects to use the net proceeds “for general corporate purposes, which may include the repayment of indebtedness.” Notes are debt securities like bonds but have a shorter term. The shares, which closed at $10. ...