For the Reaction, 2Cr²⁺ + Cl₂(g) $\rarr$ 2Cr³⁺ + 2Cl^-, E°_cell Is 1

For the reaction, 2Cr²⁺ + Cl₂(g) $\rarr$ 2Cr³⁺ + 2Cl^-, E°_cell is 1.78 V.Calculate E°_cell for the related reaction Cr³⁺ + Cl^- $\rarr$ Cr²⁺ + ¹/₂Cl₂(g) .

A) 1.78 V
B) 0.89 V
C) -1.78 V
D) -0.89 V
E) None of these.