1. The inverse demand curve for product X is given by: P_X = 25 - 0.5Q + 0.5P_Y, where P_X represents price in dollars per unit, Q represents rate of sales in pounds per week, and P_Y represents selling price of another product Y in dollars per unit. The inverse supply curve of product X is given by:

P_X = 5 + 0.5Q.

1. Let P_Y = $10. Determine the equilibrium sales and price of X.
2. Determine whether X and Y are substitutes or complements.