Answer the following questions : 

(P) The number of $p\pi -d\pi$ bonds in ${\mathrm{S}}_3{\mathrm{O}}_9$ . 

(Q) The bond order of the underlined species; ${\mathrm{NOHSO}}_4$. 

(R) The number of vacant hybrid orbitals which participate in the formation of 3-centre 2 electron bonds, i.e., banana bonds on diborane structure. 

(S) The number of intramolecular H-bonds formed in a molecule of chloral hydrate.