For the Reaction, 2Cr²⁺ + Cl₂(g) $\rarr$ 2Cr³⁺ + 2Cl^-, E ^$\circ$

For the reaction, 2Cr²⁺ + Cl₂(g) $\rarr$ 2Cr³⁺ + 2Cl^-, E ^$\circ$ _cell is 1.78 V. Calculate E ^$\circ$ _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.