If John receives a higher grade in physics than in economics and receives a higher grade in economics than in either ...

After writing down the formula I have the following G>P>E>I>R Because G and P are consecutive, G's grade is higher then P I and R are consecutive E is greater then H and in this question P is greater then E and E is greater then I & R. So I is in the D slot so why isn't that correct? I know I overlooked something because I am wrong, I just don't see what it is.