On January 1, 2015, when its $30 par value common stock was selling for $80 per share, a corporation issued $30 million of 10% convertible debentures due in 10 years. The conversion option allowed the holder of each $1,000 bond to convert it into six shares of the corporation's $30 par value common stock. The debentures were issued for $31 million. At the time of issuance, the present value of the bond payments was $28.50 million, and the corporation believes the difference between the present value and the amount paid is attributable to the conversion feature. On January 1, 2016, the corporation's $30 par value common stock was split 3 for 1. On January 1, 2017, when the corporation's $10 par value common stock was selling for $90 per share, holders of 40% of the convertible debentures exercised their conversion options. The corporation uses the straight-line method for amortizing any bond discounts or premiums.