The ripening room

Green bananas are kept in rooms with different amounts of ethylene. A table gives the days that they need to ripen. You will work out the days saved, the share saved, and a small rule for a trader.

The idea. More ethylene means fewer days. The lists are in step: the first ppm goes with the first number of days.

Your tasks.

1. Set saved to the days saved at the highest ethylene, compared with no ethylene.
2. Set saved_percent to that saving as a per cent of the days with no ethylene, rounded to a whole number.
3. Finish lowest_dose. It gives the smallest ethylene, in ppm, that ripens the fruit in fewer than limit days, or None if no dose does.