If Korea's average annual growth rate is 9 percent and that of the United States is 4 percent, the time required for Korea's real GDP to double will be ____ less than the time required for the GDP of the United States to double

_______________is a type of cost-benefit decision making that compares the extra benefits to the extra cost of an action.

Fill in the blank(s) with the appropriate word(s).

Carlson earns an income of $10,000 per month. Under the federal income tax system, the first $9,000 he earns is taxed at 10% and the remaining income is taxed at 20%. The tax owed by Carlson equals _____

a. $1,100 b. $2,000 c. $1,500 d. $3,000