7. Which of the following CNF expressions are satisfiable? If the expression is satisfiable, then give an assignment to the variables that causes the expression to evaluate to 1. If the expression is not satisfiable, then give the input/output table showing that no assignment to the variables satisfies the expression. a ( x + 2 ) ( x + y ) (3+z) b ) ( x + 2 ) ( x + y ) ( y + z ) ( x + y + 2)( x ty +z) ( source: Exercise 5.5.1: Which CNF expressions are satisfiable? (a, c))