A doctor observes a graph that shows the electrical activity (in volts) of the heart of a patient over a period of time (in seconds). Each spike corresponds to one heart beat. The doctor needs to calculate the heart rate of the patient in beats per minute. What is the heart rate of this patient? beats per minute 0.007 0.006 0.005+ 0.004 0.003 0.002 0.001-1 5​