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: find the value of 1 / ( 3 + 1 / ( 3 + 1 / ( 3 - 1 / 3 ) ) )
Options: a. 21 / 29, b. 27 / 89, c. 89 / 21, d. 29 / 21, e. none
b

Problem: a student took 5 papers in an examination, where the full marks were the same for each paper. his marks in these papers were in the proportion of 6: 7: 8: 9: 10. in all papers together, the candidate obtained 60 % of the total marks then, the number of papers in which he got more than 50 % marks is
Options: a. 1, b. 3, c. 4, d. 5, e. 7
c

Problem: tough and tricky questions: word problems. micheal, saren and donald decided to club together to buy a present. each of them gave equal amount of money. luckily saren negotiated a 20 % discount for the present so that each of them paid 4 dollars less. how much did they pay for a present ?
Options: a. 20, b. 36, c. 48, d. 60, e. 72
c