# proving that pp closed under cook reductions [closed]

I tried to prove or disprove that pp is closed under cook reductions. anyone has a idea or link to a answer?

PH $\subseteq$ PPP ​ is known to hold, so if PP is closed under Cook reductions
then ​ PH $\subseteq$ PPP $\subseteq$ PPPP $\subseteq$ PP . ​ ​ ​ ​ ( PH $\subseteq$ PP ​ is not known to hold.)