Consider a Stackelberg model in which firm 1 sets output q, and then firm 2 observes q, before setting q,. In the Subgame perfect Equlibrium, O a. Firm 1 chooses a function, and firm 2 chooses a number. O b. Both firms choose functions. O c. Both firms chooses numbers. Q d. Firm 1 chooses a number, and firm 2 chooses a function