Calculate the activation energy for the reverse reaction

[ChelseaQ]

For the decomposition of one mole of nitrosyl chloride, Delta H = 38kJ. NOCl(g)-->NO(g)+Cl2(g). The activation energy of this reaction is 100kJ. Calculate the activation energy for the reverse reaction in kJ.


I attempted this question but cannot find the process or equation to finish the question. So far I have only been able to calculate the Delta H of the product and reaction.
(NO + Cl2) - (NOCl) = (90.29 + 0) - (211.59)

I cannot figure out where to go from here and do not even know if I am starting off right..HELP PLEASE!

 

[Ygggdrasil]

Perhaps it would be helpful to draw a picture of the energies of the reactants, transition state, and products, then label the relevant energy values.