Which bests describes the purpose served by economic models within an economic systemh

Stocks a, b, and c are similar in some respects: each has an expected return of 10% and a standard deviation of 25%. stocks a and b have returns that are independent of one another; i.e., their correlation coefficient, r, equals zero. stocks a and c have returns that are negatively correlated with one another; i.e., r is less than 0. portfolio ab is a portfolio with half of its money invested in stock a and half in stock b. portfolio ac is a portfolio with half of its money invested in stock a and half invested in stock c. which of the following statements is correct? a. portfolio ab has a standard deviation that is greater than 25%.b. portfolio ac has an expected return that is less than 10%.c. portfolio ac has a standard deviation that is less than 25%.d. portfolio ab has a standard deviation that is equal to 25%.e. portfolio ac has an expected return that is greater than 25%.

Suppose farmer lane grows and sells cotton in a perfectly competitive industry. the market price of cotton is $1.64 per kilogram, and his marginal cost of production is $1.44 per kilogram, which increases with output. assume farmer lane is currently earning a profit. can farmer lane do anything to increase his profit in the short run? farmer lane: a. cannot do anything to increase his profit. b. may or may not be able to increase his profit. c. can increase his profit by raising his price. d. can increase his profit by producing more output. e. can increase his profit by shutting down.

Amazon inc. does not currently pay a dividend. analysts expect amazon to commence paying annual dividends in three years. the first dividend is expected to be $2 per share. dividends are expected to grow from that point at an annual rate of 4% in perpetuity. investors expect a 12% return from the stock. what should the price of the stock be today?