Anina's normal alveolar ventilation rate (AVR) during mild excerise is 6.0 L/min. She goes snorkeling to a beach, on a warm summer day, water is not too cold. The snorkel volume is 50 ml. Assuming this is a mild exercise for Anina, what should be her respiratory rate to maintain 6.0 L while snorkeling. ( Assume a constant tidal volume of 500 ml and anatomic dead space of 150 ml)