A producer’s supply function is given by the equation: where Qs s is the quantity of steel supplied by the market, Ps is the per-unit price of steel, and Pa is the per-unit price of aluminum. If the...

A producer’s supply function is given by the equation:

where Qs s is the quantity of steel supplied by the market, Ps is the per-unit price of steel, and Pa is the per-unit price of aluminum.

If the price of aluminum rises, what happens to the steel producer’s supply curve? The supply curve:

A. shifts to the left.

B. shifts to the right.

C. remains unchanged.