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 couple who own an appliance store discover that if they advertise a sales discount of 10 % on every item in the store, at the end of one month the number of total items sold increases 15 %. their gross income from sales for one month increases by what percent ?
Options: a. 1.5 %, b. 2.5 %, c. 3.5 %, d. 4.5 %, e. 5.5 %

A: c
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Q: Problem: what percent is 6 gm of 1 kg ?
Options: a. 1.5 %, b. 0.5 %, c. 0.6 %, d. 3.5 %, e. 4 %

A: c
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Q: Problem: a retailer bought a machine at a wholesale price of $ 90 and later on sold it after a 10 % discount of the retail price. if the retailer made a profit equivalent to 20 % of the whole price, what is the retail price r of the machine ?
Options: a. 81, b. 100, c. 120, d. 135, e. 160

A:
c
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