Which of the following statement are true? (i) The product of a positive and negative integer is negative. (ii) The product of three negative integers is a negative integer. (iii) Of the two integers, if one is negative, then their product must be positive. (iv) For all non-zero integers `a and b , axxb` is always greater than either `a or b.` (v) The product of a negative and a positive integer may be zero. (vi) There does not exist an integer `b` such that for `a gt1, axxb=bxxa=b.`