Equation for the market demand function for product

Question

Assignment:

You are given the following equation for the market demand function for product X:

Q_D = 500 - 20P_x + .0021- 10P_y

Where QD = quantity of X demanded per year

P_x = price per unit of product X

I = average income per year

P_y = price per unit of product Y

Question 1: Is X a superior (normal), neutral, or inferior good? Why?

Question 2: Is Y a substitute for, complement to, or independent of, X? Why? Assume I = $100,000 and Py = $7 in the remainder of this problem.

Question 3: What Px causes the demand for X to fall to zero?

Question 4: How much X would the market demand if X was given away for free?

Question 5: What must Px be if 50 units of X are to be sold per time period?

Question 6: Suppose Px = 10. What is the price elasticity of demand for X?