For each of the following, discuss the nature of the externalities involved and possible government responses:
a. The outbreak of SARS (sudden acute respiratory syndrome) in Toronto in 2003
b. The H1N1 flu pandemic, as declared by the World Health Organization in June 2009
c. The use of firewood, dung, charcoal, and other unimproved fuels for indoor cooking and heating in rural households in sub-Saharan Africa and China
d. Driving on a 

(i) Congested highway and 

(ii) Uncongested highway