Arrangements of cells

You will write three functions that describe a group of cells, and then find the best arrangement.

The idea. $N$ identical cells are joined in $m$ rows of $k$ cells, with $N = mk$. The group has emf $kE$ and internal resistance $kr/m$. The current through a load $R$ is the emf divided by $R$ plus the resistance of the group.

Your tasks.

1. In group_emf, return the emf of $k$ cells in series, in V.
2. In group_resistance, return the internal resistance of the group, in ohm.
3. In best_rows, find the current for every whole number $m$ that divides $N$, and return the best $m$ with its current.