Refer to the table above. If the rental price of machines is $40 per day, up to how many machines should the firm rent to maximize profits?

U.S. demand for tertiary labor increases when

(a) the wage rate rises. (b) urbanization proceeds. (c) demand for goods and services decreases. (d) price of output declines.

As the price of the U.S. dollar increases in terms of foreign currency,

a. U.S. products become cheaper for foreigners b. foreign goods become cheaper for Americans c. dollars are worth less d. the U.S. demand for foreign exchange increases e. the supply of foreign exchange to U.S. markets decreases