b
Rationale: Placing the infant under the radiant warmer is first because this allows for full observation and access of the newborn without increasing the risk for hypothermia. Placing the infant under the oxygen hood with continuous oxygen flow is second because this action addresses the primary problem. Performing the respiratory assessment third provides a baseline assessment of the primary problem. Continuous pulse oximetry is fourth because it provides a way to monitor the effectiveness of the nursing actions. The infant was separated from the mother, so breast feeding was not possible and NPO status would now need to be maintained. The chest x-ray is last because it can be obtained with the infant under the radiant warmer and after the actions to oxygenate and assess respiratory status have been implemented.

temperature: b; heart rate: a; respiration rate: a; breath sounds: b; color: b; nasal flaring: a; retractions: a
Rationale: Heart and respiratory rate have decreased, showing improvement. The absence of nasal flaring and retractions demonstrate improvement in respiratory effort, showing improvement. Temperature, breath sounds, and color are the same, therefore unchanged.