A seated normal adult breathes in and exhales every 4 seconds with a change 0.7 liter inhale and exhale. A normal adult will maintain a minimum of 1.35 liters during normal breathing. If you begin timing immediately following an exhale, then write a sinusoidal function that models the situation. How many liters will you have in the lungs at 3.5 seconds? At what time will you have 1.72 liters for the 4th time?