If the equilibrium price for ice cream decreases and the equilibrium quantity increases we conclude that a possible cause of this is that ​

Plastic and steel are substitutes in the production of body panels for certain automobiles. if the price of plastic increases, with other things remaining the same, we would expect: a) the demand curve for plastic to shift to the left. b) the price of steel to fall. c) the demand curve for steel to shift to the left d) nothing to happen to steel because it is only a substitute for plastic. e) the demand curve for steel to shift to the right