A fading pull and a stronger acid

A chlorine atom in an acid pulls electrons through the chain. You will find how much of the pull is left at a distance, and how much stronger the acid becomes when chlorine sits next to the acid group.

The idea. In a simple model each bond passes on a fixed share of the pull. The acid strength comes from the pKa: $K_a = 10^{-\text{p}K_a}$.

Your tasks.

1. Set after3 to the percentage of the pull that is left after three bonds.
2. Set ka_plain to $K_a$ of the acid without chlorine.
3. Set ka_chloro to $K_a$ of the acid with chlorine on the carbon next to the acid group.
4. Set times to how many times stronger the chlorine acid is.