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: a 24 ' ' x 24 ' ' square metal plate needs to be fixed by a carpenter on to a wooden board. the carpenter uses nails all along the edges of the square such that there are 25 nails on each side of the square. each nail is at the same distance from the neighboring nails. how many nails does the carpenter use ?
Options: ['a. 94', 'b. 95', 'c. 96', 'd. 97', 'e. 98']
c

Problem: how much more would rs. 10000 fetch, after two years, if it is put at 20 % p. a. compound interest payable half yearly than if is put at 20 % p. a. compound interest payable yearly ?
Options: a. 241, b. 725, c. 992, d. 837, e. 923
a

Problem: - - - - - - - - - - - - - - - - yes - - - - - - - - - no - - - - unsure subject m - - - - 500 - - - - - - - - 200 - - - - - 100 subject r - - - - 400 - - - - - - - - 100 - - - - - 300 a total of 800 students were asked whether they found two subjects, m and r, interesting. each answer was either yes or no or unsure, and the numbers of students who gave these answers are listed in the table above. if 140 students answered yes only for subject m, how many of the students did not answer yes for either subject ?
Options: a. 100, b. 260, c. 360, d. 400, e. 500

b