3. (4 points, 1 point each) Determine the truth value (T or F) of each of these statements if the domain of each variable consists of all integers. a. Vxy (x = y) 2 b. 3x3y (x + yy + x) c. xvy(x + y= 0) d. Vvy(((x < 0) ^ (y < 0)) (xy > 0)) 4. (4 points) Prove this is a valid argument using rules of inference and logical equivalences. Include all hypotheses in proof and state all steps use- (-pVq) S Vr (p^q) s ..r 5. (4 points) Prove that if n is an integer and 5n + 4 is even, then n is even.