Will the halogen displace the halide

You will finish a program that predicts which halogens oxidise which halide ions. It works from the standard electrode potentials.

The idea. A halogen oxidises the halide of another halogen if its potential is higher. The cell potential is the difference. A halogen with a higher potential is a stronger oxidising agent.

Your tasks.

1. Complete cell_potential(added, present) so that it returns the potential of the halogen added minus that of the other halogen, rounded to 2 decimal places.
2. Complete displaces(added, present) so that it returns True when the cell potential is positive.
3. Set strongest_first to the list of halogen names in order from the strongest oxidising agent to the weakest.