4. You are taking a ride on a paddlewheel steamboat. As the paddlewheel turns, the distance of a point on the wheel from the surface of the water surface is a sinusoidal function of time. At 8 seconds, the point is at at its highest point of 7. The wheel has a diameter of 8 , and it completes one revolution every 18 seconds. b. Write the equation of the function that represents the graph. c. Calculate the height of the point after 90 seconds