The biceps-jerk reflex employs motor neurons that exit from the spinal cord in the 5th spinal nerve

Question:

The biceps-jerk reflex employs motor neurons that exit from the spinal cord in the 5th spinal nerve (C5) that is fifth from the top of the cord. The tnceps-jerk reflex involves motor neurons in the 7th spinal nerve (C7). How might these reflexes be used to help locate the site of damage in a patient with a neck injury?