9) (10 points) Using propositional logic, prove the following is valid, justifying the steps. (Probably won't need 11 steps.) If chicken is on the menu, then don't order fish, but you should have either fish or salad. So, if chicken is on the menu, have salad. C, F, S 1) 2) 3) 4) 5) 6) 7) 9) 10) 10) (4 points) Identify the following quantifiers: 3 11) (7 points) Given the following expression: (x)Ey)P(x, y), where P(x, y) is x+y=0" give two domains of interpretation. One where the expression is true. Another where the expression is false