The task is to generate the correct answer for a given math problem.

Example Input: Problem: how much interest will $ 10,000 earn in 9 months at an annual rate of 4 % ?
Example Output: $ 300

Example Input: Problem: if the cost price of 50 articles is equal to the selling price of 40 articles , then the gain or loss percent is ?
Example Output: 25 %

Example Input: Problem: crazy eddie has a key chain factory . eddie managed to decrease the cost of manufacturing his key chains while keeping the same selling price , and thus increased the profit from the sale of each key chain from 50 % of the selling price to 50 % of the selling price . if the manufacturing cost is now $ 50 , what was it before the decrease ?
Example Output:
$ 50