Every day, the depth of water at a certain location is measured. It's found that at 9 : 00 hours (on a 24-hour clock), the tide is at its lowest depth of 456m and at 21 : 00 hours the tide is at its greatest depth of 115cm. Let f(t) be the depth of the tide-water (in centimeters) at t hours after 0 : 00 (midnight) on any given day. We can express f(t) = acos(b(t 7 h)) + k where: The amplitude is a =0 cm. The centre axis is y = k for k :[3 cm. The period is p 2C] hours and therefore b :0. The first non-negative maximum (and therefore the shift) occurs at h :C]. N) :[3 Find the expected depth of the tide at 22 : 00 on an arbitrary day. The expected depth is: [3 cm