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ECON1003 S1 2023

Problem Set 2

1. Solve the following quadratic equations.

(a) x2 − 6x + 5 = 0

(b) Q2 + 6Q + 5 = 0

(c) 2/(P + 1) = (P – 1)/6

(d) Q/2 + 12/Q = 5

2. The demand function for a good is given by Q = (200/P) − 1 and the (inverse) supply functions is P = 5 + 0.5Q. Solve for the equilibrium level of P and Q.

3. Consider a monopolist who faces an inverse demand function P = 10 − Q and no production costs.

(a) Compute total revenue (TR).

(b) Plot total revenue as a function of Q.

(c) Find the points Q at which the monopolist breaks even.

4. Solve the following equations. (a) 2x /4 = 2.

(b) e5x = 1/ ex−5

(c) 2 + ln(t − 5) = 2.5

5. The spread of a carrot fly through an untreated crop is modelled by the equation Y = 500(1 − e−0.5t), where Y is the weight of infected carrots in tons, t is time in days.

(a) Graph Y for as a function t in the interval [0, 6]. Hence describe the spread of carrot fly during the next 6 days.

(b) Calculate the time taken to infect 300 tons of carrots.

6. Consider a utility maximization problem that we briefly touched up in Lecture 1. Let   the consumer’s utility function be given by U(x1, x2) = x1x2. This functional form is called the Cobb Douglas utility function.

(a) Fix the level of utility at 25. Plot the consumer’s indifference curve for this level of   utility with x1 on the horizontal axis and x2 on the vertical axis this is the collection of all points (x1, x2) such that the consumer’s utility remains constant.

(b) On the same graph, plot the budget line for p1 = p2 = 1 and m = 10.

(c) Consider the point at which these two plots touch. What happens at this point relative to other points on the budget line.