(i) Define externalities.
Externalities refer to the unintended side effects of economic activities on third parties that are not directly involved in the production or consumption of goods or services. These can be either:
Positive Externalities: Benefits to third parties (e.g., planting trees improving air quality).
Negative Externalities: Costs to third parties (e.g., pollution affecting nearby residents).

Draw a rough sketch for the curve $y = 2 + |x + 1|$. Using integration, find the area of the region bounded by the curve $y = 2 + |x + 1|$, $x = -4$, $x = 3$, and $y = 0$.
Study the given molecular structure of double-stranded polynucleotide chain of DNA and answer the questions that follow. 
(a) How many phosphodiester bonds are present in the given double-stranded polynucleotide chain?
(b) How many base pairs are there in each helical turn of double helix structure of DNA? Also write the distance between a base pair in a helix.
(c) In addition to H-bonds, what confers additional stability to the helical structure of DNA?
