Emar is on the second floor of a building and begins walking continuously up and down the stairway that connects the two floors. The stairway has a slope defined by an equation and it takes Emar 75 seconds to travel between floors. As he walks, his height follows a sinusoidal pattern over time. Sophia is also on the stairway and is moving down at a steady velocity. The question asks to determine the equation for Emar's height over time, calculate the height the two will be at the same spot, and count the possible combinations of selected people at a given time.