The productivity ledger

You will write functions for the net primary productivity, for the share of the GPP that the plants respire, and for the most productive place.

The idea. $\text{NPP} = \text{GPP} - R$. The share is $R / \text{GPP}$ times $100$. A place is a pair (gpp, r).

Your tasks.

1. Finish npp. It gives the net primary productivity.
2. Finish respired_share. It gives the per cent of the GPP that is respired.
3. Finish best_place. It gives the name of the place with the largest NPP.