The inverse demand curve for product X is given by:
PX = 25 - 0.005Q + 0.15PY
where PX represents price in dollars per unit, Q represents rate of sales in pounds per week, and PY represents selling price of another product Y in dollars per unit. The inverse supply curve of product X is given by:
PX = 5 + 0.004Q
a. Determine the equilibrium price and sales of X. Let PY = $10
b. Determine whether X and Y are substitutes or complements.