Externalties - try out these websites and trial questions

http://tutor2u.net/economics/content/topics/externalities/positive_externalities.htm

http://www.basiceconomics.info/market-failures-and-externalities.php

Possible questions:

Explain why negative externalities lead to inefficient overproduction and how property rights, emission charges, marketable permits, and taxes can be used to achieve a more efficient outcome.

Explain why positive externalities lead to inefficient underproduction and how public provision, subsidies, vouchers, and patents can increase economic efficiency.