Suppose a monopoly concrete contractor builds 20 driveways per month for $10,000 each. In order to increase sales to 21 driveways, the contractor must lower the price of driveways to $9,500. The marginal revenue of the 21st driveway is:.
a. $500.
b. $199,500.
c. -$500.
d. $9,500.

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?