Consider the following reactions in which all the reactants and the products are in gaseous state.
`2PQ hArr P_(2)=Q_(2), K_(1)=2.5xx10^(5)`
`PQ +1//2 R_(2) hArr PQR, K_92) =5xx10^(-3)`
The value of `K_(2)` for the equilibrium
`1//2P_(2)+1//2Q_(2) +1//2R_(2) hArr PQR,` is