The depth of water near a boat dock is collected by a buoy. The data shows that the water level reached 11 ft. during high tide at 2:00 am and a level of 8 ft. during low tide at 9:00 am. The depth can be modeled by a sinusoidal function.

a. How deep will the water be at noon?
b. For approximately what times will the water level be less than 9 ft?