Enthalpy of formation of (C=C) and (C-C) in $C_2H_4$ is -590 kJ/mol and -331 kJ/mol, respectively. What is the enthalpy change when ethylene polymerises to form polythene?

Question

(a) +259 kJ/mol
(b) +72 kJ/mol
(c) -259 kJ/mol
(d) -72 kJ/mol