1) The market demand function of a commodity is represented by Qx = 20-2Px -0.5Py + 0.01M; where Qx is quantity demanded for commodity X, Px is the price of commodity X, Py is the price of commodity Y and M is the consumer's income.

I) Calculate price and cross elasticities of demand for commodity X when Px =5, Py=10 and M =1000.

2)For a product produced by a firm demand is given by the expression: P = 40 - 2Q. Fixed cost is 10. Variable costs of producing Q units are VC (Q) = Q^2 + 5Q.

(a) Find expressions for total, average and marginal costs.

(b) Find expressions for total, average and marginal revenue.

(c) Sketch the graph for demand, marginal revenue and marginal cost curves

3) Maximize profits for a firm, given total revenue

TR = 4000Q - 33Q^2

and total cost

TC = 2Q^3 -3Q^2 + 400Q + 5000,

assuming Q > 0