For maximum benefit, you should exercise 5-7 times a week for 60 minutes and your heart rate should be between of your max heart rate.

60 to 80%

Explanation:

For maximum benefit, the heart rates during exercise regimes should be between 60 to 80% of an individual's maximum heart rate.

The maximum heart rate varies from individuals to individuals and largely depends on age. It is calculated by subtracting one's age from 220. For example, a person that is 40 years old would have a maximum heart rate of;

  220 - 40 = 180 beats per minute.

Such a person's heart rates during exercises should be between 108 and 144 beats per minute for maximum benefits.

answer: b.

explanation: