12. The following events occur one at a time: (i) The price of crude oil rises. (ii) The price of a car rises. (iii) All speed limits on highways are abolished. (iv) Robots cut car production costs. Which of these events will increase or decrease (state which occurs)

a. The demand for gasoline?

b. The supply of gasoline?

c. The quantity of gasoline demanded?

d. The quantity of gasoline supplied?