Fill in the blanks to make the following statements correct.

a. An important aspect of Neoclassical growth theory is that increases in the supply of one factor, all else held constant, imply eventually _________ marginal returns to that factor.

b. In Neoclassical growth theory, an increase in the labour force alone ________ total output and _________ the level of per capita output.

c. When a new and better harvesting machine replaces an old harvesting machine on a farm and is more productive than the old one, we say there has been technical change.

d. Some newer growth theories are based on the assumption that technological change is _________ to the economic system; others are based on the possibility that there are ________ marginal returns to investment.

e. Neoclassical growth theories are pessimistic because they emphasize ________ returns with a given state of ___________ . Modern growth theories are more optimistic because they emphasize the unlimited potential of _________ .