Two oligopolists must simultaneously decide upon a pricing strategy, either set a high price (Ph) or a low price (Pl). Once the price is set, it cannot be changed. If the firms can successfully collude, the outcome of the game will be:

(A) both firms set a low price.

(B) both Firm Y and Firm Z alternate between the high price and low price.
(C) both firms set a high price.
(D) Firm Y sets the high price and Firm Z sets the low price.
(E) Firm Y sets the low price and Firm Z sets the high price.