If disposable income increases by $500 million, and consumption increases by $400 million, then the marginal propensity to consume is

In the foreign exchange market, the supply curve for dollars slopes upwards because

A) as the exchange rate rises, imports become more expensive, and more dollars are supplied to pay for the imports. B) as the exchange rate rises, imports become cheaper, and more dollars are supplied to pay for the increase in the quantity of imports. C) as the exchange rate rises, more dollars are supplied since the profit from selling dollars falls. D) supply curves always slope upwards.

In the above figure, after the second worker is hired, the marginal product of labor is

A) increasing. B) diminishing. C) constant. D) zero.