In: Economics
A consumer’s utility is given by ?(?, ?) = ? ^1/2? ^1/4 where Z is the consumption of pizza and C is the consumption of coffee. Let pZ and pC denote the prices of pizza and coffee, and let m be the consumer’s income.
(a) State the “optimality condition” characterizing the best affordable bundle.
(b) Derive the consumer’s demands for pizza and coffee. You must show your work.
(c) What is the consumer’s optimal consumption if ?? = ?? = 1 and m=120? ? ∗ =_________ ? ∗ =_________
(d) Suppose that the price of coffee rises to ?? = 2 and at the same time income increases to m=160? Is the bundle (? ∗ , ? ∗ ) in (c) still affordable? Is the consumer off or worse off as a result of the change in price and income?
Consumer's utility function;
U(z,c) = z1/2 c1/4
where, z = pizza
c = coffee
Prices of pizza = Pz
Prices of coffee = Pc
Consumer's income = M
(a) The optimal level is achieved when the slope of indifference curve (MRS) is equal to the slope of budget line (Pz/Pc);
MRS = Pz/Pc
Marginal rate of substitution (MRS) : It is the rate at which a consumer is willing to give up some units of one good in order to gain one more unit of another good. It is calculated as;
MRS = MUz / MUc
MUz = d/dz (z1/2
c1/4)
MUz = c1/4 / 2z1/2
MUc = d/dc(z1/2
c1/4)
MUc = z1/2 / 4c3/4
MRS = (c1/4 /
2z1/2) / (z1/2 / 4c3/4)
= 4c / 2z
MRS = 2c/z
At optimal level;
MRS =
Pz/Pc
2c/z = Pz/Pc
2c = zPz/Pc
c = zPz/2Pc
(b) Consumer's demand will be;
c = zPz/2Pc
Putting in the budget constraint;
Pzz + Pcc =
M
Pzz + Pc (zPz/2Pc) =
M
Pzz + Pzz/2 = M
2Pzz + Pzz = 2M
3Pzz = 2M
z = 2M/3Pz
c = (2M/Pz)Pz /
2Pc
c = 2M / 2Pc
c = M/ Pc
The demand function for pizza will be; z = 2M/3Pz
The demand function for coffee will be; c = M/ Pc
(c) Given;
Prices of pizza; Pz = 1
Prices of coffee; Pc = 1
Consumer's income; M = 120
So, optimal bundle will be;
c = M/ Pc
c = 120/1
c = 120
z = 2M/3Pz
z = 2*120 / 3
z = 80
(d) Now, price of coffee rises to; P'c = 2
Consumer's income increases to; M' = 160
Now, the optimal consumption bundle will be;
c = M'/ P'c
c = 160/2
c' = 80
z = 2M'/3Pz
= 2(160) / 3(1)
= 320/3
z' = 106.67
Utility before change in price and income;
U(z,c) = z1/2
c1/4
U(120,80) = 1201/2 801/4
U(120,80) = 13.94
Utility after change in price and income;
U(z,c) = z1/2
c1/4
U(80,106.67) = 801/2 106.671/4
U(80,106.67) = 12.16
As we can see, after the changes in price and income consumer's utility decreases from 13.94 to 12.16. Thus, we can say that consumer is worse off.