CAT 2017 Question | Increase in profit

#CAT2017 Question:
If a seller gives a discount of 15% on retail price, she still makes a profit of 2%. Which of the following ensures that she makes a profit of 20%?
A) Give a discount of 5% on retail price
B) Give a discount of 2% on retail price
C) Increase the retail price by 2%
D) Sell at retail price

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Best wishes for CAT preparation.