If $\mathrm{V}$ is the volume of one molecule of a gas, Van der Waals constant $\text{'}\mathrm{b}\text{'}$ is: (${\mathrm{N}}_{\mathrm{o}}$=Avogadro's number)

The Van der Waals parameters for gases

W X, Y and Z are

Which one of these gases has the highest critical temperature?

$\left(\mathrm{a}\right)$ ${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)\rightleftharpoons {\mathrm{CuSO}}_4.3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$    ${\mathrm{K}}_{\mathrm{p}}=4\times {10}^{-4} {\mathrm{atm}}^2$

$\left(\mathrm{b}\right)$ ${\mathrm{Na}}_2{\mathrm{SO}}_4.10{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)\rightleftharpoons {\mathrm{Na}}_2{\mathrm{SO}}_4.5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)+5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$    ${\mathrm{K}}_{\mathrm{p}}=2.43\times {10}^{-9} {\mathrm{atm}}^5$

$\left(\mathrm{c}\right)$ ${\mathrm{Na}}_2{\mathrm{S}}_2{\mathrm{O}}_3.5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)\rightleftharpoons {\mathrm{Na}}_2{\mathrm{S}}_2{\mathrm{O}}_3.2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$    ${\mathrm{K}}_{\mathrm{p}}=6.4\times {10}^{-5} {\mathrm{atm}}^3$

What is the order of partial pressure of water vapours at equilibrium and relative humidity respectively?