Question

I posted this question last night but did not get an answer- I am posting again because I have an exam I am studying for and do not understand this concept! Thanks!
Using the given data, and the table of Standard Reduction Potentials, find the standard reduction potential for this half reaction:
8H^+ + BaCrO4(s) + 3e- -> Ba^2+ + Cr^3+ + 4H2O(l)

given:
Ksp (BaCrO4)=2.1E-10
DeltaGf* (kJ/mol): CrO4^2- (-727.75), Cr2O7^2- (-1301.1), H+ (0), H2O(l) (-237.19)


Please help! =