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.

Q: Problem: a shop owner professes to sell his articles at certain cost price but he uses false weights with which he cheats by 12 % while buying and by 30 % while selling. what is his percentage profit ?
Options: a. 10.22 %, b. 20.22 %, c. 21.22 %, d. 60 %, e. ca n ' t be calculated

A: d
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Q: Problem: set a contains all the even numbers between 2 and 50 inclusive. set b contains all the even numbers between 62 and 110 inclusive. what is the difference between the sum of elements of set b and the sum of the elements of set a ?
Options: a. 1500, b. 3100, c. 4400, d. 6200, e. 7400

A: a
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Q: Problem: the weight of every type a widget is the same, the weight of every type b widget is the same, and the weight of every type c widget is the same. if the weight of 7 type a widgets is equal to the weight of 4 type b widgets, and the weight of 3 type b widgets is equal to the weight of 7 type c widgets. what is the ratio of the total weight of 1 type a widget and 1 type b widget, to the total weight of 1 type b widget and 1 type c widget ?
Options: a. 5: 4, b. 7: 6, c. 9: 8, d. 11: 10, e. 13: 12

A:
d
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