In what year did sales of gold for investment exceed that for jewelry for the first time?

The group of countries more likely to have a high number of telephone lines per 1,000 people is

a. high-income countries b. zero-income countries c. infinite-income countries d. low-income countries e. middle-income countries

Table 21.4Output (Units per Day)Total Cost (Dollars per Day)016130242358478The marginal cost of the fourth unit of output in Table 21.4 is

A. $20.00. B. $16.00. C. $4.00. D. $19.50.