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

Example Input: Problem: if a - b = 6 and a 2 + b 2 = 50 , find the value of ab .
Example Output: a ) 7

Example Input: Problem: if a = 105 and a ^ 3 = 21 × 25 × 45 × z , what is the value of z ?
Example Output: 49

Example Input: Problem: a certain telephone company offers two plans , a and b . under plan a , the company charges a total of $ 0.60 for the first 9 minutes of each call and $ 0.06 per minute thereafter . under plan b , the company charges $ 0.08 per minute of each call . what is the duration of a call , in minutes , for which the company charges the same amount under plan a and under plan b ?
Example Output:
3