Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

Problem: if the population of a certain country increases at the rate of one person every 15 seconds, by how many persons does the population increase in 25 minutes ?
Options: a. 80, b. 100, c. 150, d. 240, e. 300
b

Problem: one side of a rectangular field is 14 m and one of its diagonal is 17 m. find the area of the field.
Options: a. 134.4, b. 120, c. 150, d. 180, e. none
a

Problem: it is decided to construct a 2 metre broad pathway around a rectangular plot on the inside. if the area of the plots is 96 sq. m. and the rate of construction is rs. 50 per square metre., what will be the total cost of the construction ?
Options: ['a. rs. 3500', 'b. rs. 4200', 'c. insufficient data', 'd. rs. 4400', 'e. none of these']
c