[5 points each] Mark each statement true or false. If it is true, justify your answer clearly by making references to the results seen in class. If it is false, give a counter-example. (a) If the sum of the second and fourth row vectors of a 6 x 6 matrix A is equal to the last row vector, then det A=0. (b) If A is a square matrix with two identical columns, then det(A) = 0