Assume that () 1 -1 1 | y (x, y, z) = -1 1 -1 1 -1 1 where the left-hand side is the the product of two matrices. If a = (x, y, z), then the value || a ||2 is equal to (a) 1 (b) 2 (c) 3 (d) 4 (e) None of these