In a square matrix A of order 3 each element `a_(i i)` is equal to the sum of the roots of the equation `x^2-(a+b)x+a b=0` each `a_(i ,i+1)` is equal to the product of the roots, each `a_(i ,i-1)` is unity and the rest of the elements are all zero. The value of the `|A|` is equal to 0 (b) `(a+b)^3` `a^3-b^3` (d) `(a^2+b^2)(a+b)`