The table at the right shows the times for high tide and low tide of one day. The markings on the side of a local pier showed a high tide of 7ft and a low tide of 4 ft on the previous day.

c. Write a cosine function that models the relationship between the depth of water and the time of day.
Use y=0 to represent the average depth of water.
Use t=0 to represent the time 4:03 A.M.