[MaximumCupcakes]

Here's the problem:

A chemical reaction at 1.0 bar and 298 K has ΔrG° = -335 kJ/mol. The Gibbs function of the reactants changes by +7.5 kJ/mol when the pressure is changed from 1.0 bar to some other pressure P2. The products change by +8.4 kJ/mol over the same pressure change, 1.0 bar to P2. What is ΔrG° at P2 and 298 K?

Relevant equations (Maybe?):

ΔG = ΔG° + RTln(P₂/P₁)

I'm not sure what to do with the Gibbs functions of the reactants and products. Can I subtract reactants from products (8.4 - 7.5) to get ΔrG? I did this and plugged all of the numbers into the above formula, solving for P₂ = 7.52 bar. What now? Am I on the right track at all?