Consider a Voltaic Cell Based on the Following Cell Reaction $\rarr$

Consider a voltaic cell based on the following cell reaction: Ni(s) + At₂(s) $\rarr$ Ni²⁺(aq) + 2At^- (aq)
Given that the standard cell emf is 0.55 V, what is the standard reduction potential for astatine? [E°(Ni²⁺/Ni) = -0.25 V]

A) 0.80 V
B) 0.30 V
C) -0.30 V
D) -0.80 V
E) 0.43 V