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ECONOMICS 301 – 001

Section #2 Exercises

1.          Each week, three rational, utility-maximizing individuals (Bill, Mary, and Jane) select quantities of two goods, X and Y, to consume that will make them as happy as they can while staying within their budgets.  Each also spends      his/her entire income on these two goods each week.

a.          Bill’s choices are represented by the following table:

 

X

Y

PX

PY

I

Week One

10

20

2

1

40

Week Two

7

19

3

1

40

Week Three

8

31

3

1

55

Did Bill’s utility increase or decrease between Week One & Week Two?          Between Week One and Week Three?  Explain using a graph in your answer. Can revealed preference arguments help here?  Why or why not?

b.          Mary’s choices are represented by the following table:

 

X

Y

PX

PY

I

Week One

10

20

2

1

40

Week Two

6

14

2

2

40

Week Three

20

10

2

2

60

Did Mary’s utility increase or decrease between Week One and Week Three? Does Mary consider both goods to be normal?  Why or why not?  Explain.

c.          Jane’s choices are represented by the following table:

 

X

Y

PX

PY

I

Week One

12

24

2

1

48

Week Two

16

32

1

1

48

Week Three

12

24

1

1

36

Plot Jane’s three chosen bundles on a well-labeled graph.  What can be said    about Jane’s preferences in this case?  Provide an expression for Jane’s utility function in this case.  Document the magnitude and direction of the                   substitution and income effects that result from a drop in the price of X from $2 / unit to  $1 / unit.

2.          Sam & Barb derive utility from leisure (N) , in hours, and the amount of the   composite good ( G ) they consume.  In order to maximize utility, they need   to allocate the 24 hours of their days between taking leisure and working for an hourly wage rate ( w ).  They have NO non-wage income.  Assume the         price of the composite good is  $1 / unit of G .  The following table                     summarizes their choices under different wage rates:

w (in $ / hour )                         Sam’s N (in hours)                   Barb’s N (in hours)

 

8                                                    16                                                 14

9                                                    15                                                 14

10                                                 14                                                 15

11                                                 14                                                 16

On well-labeled indifference curve diagrams, show each person’s optimal       choices.  Assume each has strictly monotonic and strictly convex preferences for leisure and the composite good.  Further assume they both view both        goods as normal.  Comment on the relative magnitudes of the substitution     and income effects of each wage change for each person.

Now, construct a labor supply curve for each person (separate diagrams of course).  Does each person’s labor supply curve have a perfectly inelastic    portion here?  Why?  Explain.  Does each person’s labor supply curve have both an upward sloping and a downward-sloping portion here?  Why?         Explain.

3.          Return to our Fisher model of consumption today/consumption tomorrow. If we continue to assume individuals have strictly convex preferences for    those two goods and face the same interest rate for borrowing and lending, draw diagrams for each of the situations below:

a.          A consumer who is optimizing by borrowing today responds to an increase in the interest rate by becoming a lender today.

b.          A consumer who is optimizing by lending today responds to an increase in the interest rate by choosing the Polonius Point.

c.          A consumer who is optimizing by borrowing today responds to an increase in the interest rate by choosing the Polonius Point.

Do any of these situations violate revealed preference theory?  If so, why?  If not, why not?  Explain.

4.          Natasha’s utility function is given by  U ( I )  =  [ 10 * I ]1/2 , where  I represents her annual income in thousands of dollars.

a.          Is Natasha risk loving, risk neutral, or risk averse?  Explain.

b.          Natasha’s income is currently $40,000 and she can earn that income    next year with certainty.  She is offered a chance to take a new job that offers a 0.6 probability of earning $44,000 and a 0.4 probability of        earning $33,000.  Should she take the new job?  Can you support your answer here by calculating the expected salary of that new job?

c.          For the situation in (b), would Natasha be willing to pay for insurance that guaranteed her the expected salary of that new job?  If so, how     much?  [Hint:  Calculate the risk premium of that new job.]

5.          Suppose that a firm’s production function is: q = 10*L1/2 K1/2

The cost of a unit of labor is $20 and the cost of a unit of capital is $80.

a.          The firm is currently producing 100 units of output and has determined that the cost-minimizing way of producing this output level is to use 20 units of   labor and 5 units of capital.  Show that they are indeed cost-minimizing.

Graphically illustrate this situation using isoquant and isocost lines.  Derive mathematical expressions for both as well, and label slopes and intercepts  appropriately.

b.          The firm now wants to increase output to 140 units.

What combination of L  and  K  minimizes the cost of producing 140 units?   Assume the prices of the two inputs do not change.  How would your answer change is capital is fixed to  5  units (as it would be in the short run, for           example)?

What is the total cost of producing 140 units in both cases, namely when the level of capital can be varied and when it is fixed?  Explain these differences in total cost.

Finally, in SEPARATE diagrams, show the output expansion path if:

i.           Capital and labor are both variable inputs.

ii.          Capital is fixed (at  5 units, remember) and labor continues to be a variable input.