5. Compute the weakest precondition for each of the following assignment statements and postconditions: a, a = a + 2 * b-1(a > 1} b. x = 2 * y + x-1(x > 11} c, a = 2 * b + 1; d. if (x > y) y=2*x+1 else 6. Write a brief analysis of the following semantics techniques: Attribute Grammars, operational semantics, denotational semantics 7. Prove the following program is correct: In>0> count = n; sum 0; while count 0 do sum-sum +count count= count- 1; end {sum = 1 + 2 + . . . + n}