The Following Galvanic Cell Has a Measured Cell Potential E°_cell

Multiple Choice

The following galvanic cell has a measured cell potential E°_cell = 0.646 V.
Pt(s) ∣ Sn⁴⁺(aq) ,Sn²⁺(aq) Ag⁺(aq) ∣ Ag(s)
Given that the standard reduction potential for the reduction of Ag⁺(aq) to Ag(s) is +0.800 V,what is the standard reduction potential for the Sn⁴⁺/Sn²⁺ half-reaction?

A) +0.154 V
B) -0.154 V
C) +1.45 V
D) -1.45 V
E) +0.308 V