Refer to Table 2-18. What is Mickey's opportunity cost of making an umbrella?

If there is a positive relationship between two variables,

A) the graph of the relationship will be downward sloping. B) the graph of the relationship will be upward sloping. C) the slope of the line graphing the relationship will be negative. D) Both answers A and C are correct. E) Both answers B and C are correct.

Attaining higher and higher levels of air cleanliness causes

A) additional costs to rise to increasingly high levels. B) larger and larger increases in per capita incomes. C) additional costs to fall to lower and lower levels. D) larger and larger marginal benefits to society.