The water depth at the end of a pier varies from 4 feet to 13 feet, depending on the time of low and high tides. On Wednesday, a high tide occurs at 10:00 a.m., and the next high tide occurs at 11 pm. What cosine function expresses the depth of the water H(t) as a function of time, t, in hours, since midnight on Wednesday morning? a) Find the height of the water at 1:00 p.m. b) Find the amount of hours from 10:00 a.m. that the height of the water is 10 feet.