$A\left|A^{+}(x M)\right|\left|B^{+}(y M)\right| B$

The EMF of cell is $+0.20$ V. So, cell reaction is

possible. The half-cell reactions are given as follows

(i) At negative pole

$A \rightarrow A^{+}+e^{-} \quad \text { (oxidation) }$

(ii) At positive pole

$B^{+}+e^{-} \rightarrow B \quad \text { (reduction) }$

Hence, cell reaction is

$A+B^{+} \rightarrow A^{+}+B, E_{c e l l}^{0}=+0.20 V$