I've attached the assignment. I think the sum is getting me very confused. Since it sums to one, wouldn't it just be a factor of 1 to I(x_{-}x_{n})? That can't be right, because otherwise I'm sure it wouldn't have been included, but I am stuck. I am also thrown at the I before (x-xn). Does anyone know where that would have come from? Any help would be greatly appreciated!