Consider the market for cars. Which determinant of supply is affected by each of the following events? Choose from: prices of related goods, technology, prices of inputs, expectations, and the number of sellers in the market.

a. A steel tariff increases the price of steel.

b. Improvements in robotics increase efficiency and reduce costs.

c. Factories close because of an economic downturn.

d. The government announces a plan to offer tax rebates for the purchase of commuter rail tickets.

e. The price of trucks falls, so factories produce more cars.

f. The government announces that it will dramatically rewrite efficiency standards, making it much harder for automakers to produce their cars.