4. Agatha Christie and Arthur Conan Doyle are the only two editors of mystery novels in the city of Readville.If Agatha Christie and Arthur Conan Doyle collude to earn more profits, they would:

a) each reduce the number of books published and raise prices.

b) each reduce the number of books published and lower prices.

c) each increase the number of books published and raise prices.

d) each increase the number of books published and lower prices.