A clinician is monitoring a patient's cardiovascular health during a diagnostic treadmill test. The patient's electrocardiogram (ECG) trace shows a regular sinus rhythm with an average distance of 3.75 large grid squares between consecutive R-wave peaks as shown below.
If the ECG machine operates at standard calibration where each large square represents 0.20 s, calculate the patient's heart rate in beats per minute (bpm).
16 bpm16\text{ bpm}16 bpm
80 bpm80\text{ bpm}80 bpm
400 bpm400\text{ bpm}400 bpm
1.33 bpm1.33\text{ bpm}1.33 bpm