What is the cell potential, in V, of the reaction below?

$${{\text{I}}_2} + {\text{2}}{{\text{S}}_2}{\text{O}}_3^{2 - } \to {\text{2}}{{\text{I}}^ - } + {{\text{S}}_4}{\text{O}}_6^{2 - }$$

     $\frac{1}{2}{{\text{S}}_4}{\text{O}}_6^{2 - }{\text{(aq)}} + {{\text{e}}^ - } \rightleftharpoons {{\text{S}}_2}{\text{O}}_3^{2 - }{\text{(aq)}}$     ${E^\Theta } =  + 0.09{\text{ V}}$

     ${{\text{I}}_2}{\text{(aq)}} + {\text{2}}{{\text{e}}^ - } \rightleftharpoons {\text{2}}{{\text{I}}^ - }{\text{(aq)}}$     ${E^\Theta } =  + 0.54{\text{ V}}$

A.     $+ 0.63$

B.     $+ 0.45$

C.     $- 0.45$

D.     $- 0.63$

B