Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): When using the Karvonen's formula, the exercise heart rate is higher than when using the maximum heart rate alone for a 40 years old male having a resting heart rate of 80 bpm.
Reason (R): Karvonen's formula is based on the heart rate reserve which is the difference between the maximum heart rate and the exercise heart rate.
In the light of the above statements, choose the most appropriate answer.