#puzzle50

[jdgmiles]

#50 Enclose the Most Valuable Region

A wealthy sultan promises you all the land you can enclose in a 100km fence, beginning and ending at his palace.

Land more than 20km north of the palace is rich in oil and worth $2m per km2.

All other land in the kingdom is worth $1m per km2.

What shape maximises the value of the sultan's present to you?