can anyone answer this economic questions? externality

Each of the following situations creates an externality. State the nature of the externality (positive or negative). Explain who benefits (does not pay) and who pays.

(a) a pie shop producing high fat pies
(b) customers who smoke in a restaurant
(c) drunken clientele from one restaurant disturbing others in the Viaduct Basin area
(d) a hotel that does extensive research and makes it freely available to other hotels