The reaction of ethylene (C2H4) with butadiene (C4H6=) to form cyclohexene (C6H10) has an activation energy (Ea) of 115 kJ/mol. The reverse reaction (decomposition of cyclohexene to ethylene and butadiene)

The reaction of ethylene (C2H4) with butadiene (C4H6=) to form cyclohexene (C6H10) has an activation energy (Ea) of 115 kJ/mol. The reverse reaction (decomposition of cyclohexene to ethylene and butadiene) has an activation energy of 287 kJ/mol. What is the heat of reaction, Δ Hrxn, for the forward reaction?
A) +115 kJ/mol
B) +287 kJ/mol
C) -287 kJ/mol
D) +172 kJ/mol
E) -172 kJ/mol