ECO - The generalized demand and supply functions for good X

The generalized demand and supply functions for good X are

Qd = 638 – 8P + 0.005M – 4PY Qs = 300 + 3P
Where

QD = quantity demanded of good X
P = price of good X
M = consumer income
PY = price of good Y


QS = quantity supplied of good X
P = price of good X

a. Are good X and good Y substitutes or complements? How do you know?

b. Is good X a normal good or an inferior good? How do you know?

c. What is the demand function when M = $15,000, PY = $20?

d. Solve for the equilibrium price (Po) and the equilibrium quantity (Qo).

e. Suppose that, on average, consumer income rises to $20,000. Solve for the new equilibrium price (P1) and the new equilibrium quantity (Q1).