The correct order of the rate of reaction of the following reactants with nucleophile by \( \mathrm{S_N1} \) mechanism is:
(Given: Structures I and II are rigid) 
| LIST I | LIST II | ||
|---|---|---|---|
| A | Lyman | I | Near IR |
| B | Balmer | II | Far IR |
| C | Paschen | III | Visible |
| D | p-fund | IV | UV |

Consider the following reaction sequence.

One mole each of \(A_2(g)\) and \(B_2(g)\) are taken in a 1 L closed flask and allowed to establish the equilibrium at 500 K: \(A_{2}(g)+B_{2}(g) \rightleftharpoons 2AB(g)\). The value of x (missing enthalpy of \(B_2\) or related parameter) is ______ . (Nearest integer)}