For the hypothetical electrochemical cell given below:

A | A⁺(x M) || B⁺(y M) | B .

The measured cell emf is +0.20 V. Find the overall cell reaction.

1. A⁺ + B → A + B⁺

2.  A⁺ + e^- → A ; B⁺ + e^- → B

3. The cell reaction cannot be predicted.

4. A + B⁺ → A⁺ + B