The reason why retained earnings have a cost equal to rs is because investors think they can (i. e., expect to) earn rs on investments with the same risk as the firm's common stock, and if the firm does not think that it can earn rs on the earnings that it retains, it should pay those earnings out to its investors. Thus, the cost of retained earnings is based on the opportunity cost principle.

The following pertains to smoke, inc.’s investment in debt securities: on december 31, year 3, smoke reclassified a security acquired during the year for $70,000. it had a $50,000 fair value when it was reclassified from trading to available-for-sale. an available-for-sale security costing $75,000, written down to $30,000 in year 2 because of an other-than-temporary impairment of fair value, had a $60,000 fair value on december 31, year 3. what is the net effect of the above items on smoke’s net income for the year ended december 31, year 3?