The microbe desk

A table gives the group and the job of seven microbes of the chapter. You will write functions that look things up in it, and one function for the urea that a biofertiliser saves.

The idea. A dictionary holds each microbe with its group and its job. A function can pick out the microbes of one group, or the ones whose job is a certain one.

Your tasks.

1. Finish group_of. It gives the group of a microbe.
2. Finish names_in_group. It gives the sorted list of the microbes of a group.
3. Finish nitrogen_fixers. It gives the sorted list of the microbes whose job has the word nitrogen in it.
4. Finish urea_saved. It gives the kg of urea saved on a field, with $46\%$ nitrogen in urea.