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

Example Input: Problem: bob wants to run a mile in the same time as his sister . if bob ’ s time for a mile is currently 11 minutes 20 seconds and his sister ’ s time is currently 9 minutes 36 seconds , by what percent does bob need to improve his time in order run a mile in the same time as his sister ?
Example Output: 15 

Example Input: Problem: if the personal income tax rate is lowered from 46 % to 32 % , what is the differential savings for a tax payer having an annual income before tax to the tune of $ 36000 ?
Example Output: $ 5040

Example Input: Problem: 90 kg of an alloy a is mixed with 140 kg of alloy b . if alloy a has lead and tin in the ratio 3 : 4 and alloy b has tin and copper in the ratio 2 : 5 , then the amount of tin in the new alloy is ?
Example Output:
91.4 kg