The task is to generate the correct answer for a given math problem.
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Question: Problem: a and b can do a piece of work in 7 days . with the help of c they finish the work in 5 days . c alone can do that piece of work in ?

Answer: 30 days


Question: Problem: the population of a city is 415600 . it increased by 25 % in the first year and decreased by 30 % in the second year . what is the population of the city at the end of second year ?

Answer: 363650


Question: Problem: a merchant sells an item at a 20 % discount , but still makes a gross profit of 20 percent of the cost . what percent of the cost would the gross profit on the item have been if it had been sold without the discount ?

Answer:
50 %