An increase in the exchange rate between one currency and other currencies under a fixed exchange rate system is called:

a.depreciation.

b.appreciation.

c.speculation.

d.devaluation.

e.revaluation.

A firm increases the number of hours its workers are employed from 7000 to 8000, and output increases from 140 000 bushels to 155 000 bushels. The marginal product of an extra hour is:

a.15.

b.100.

c.20.

d.10.

e.5.