Write a cosine function that models the oscillation of Eastport’s tides if their amplitude is 9 feet 8 inches, the equilibrium point is 12 feet 3 inches, the phase shift is -2.68 hours, and the period is 12.34 hours.

How exactly do I do this? I've only written Sinusoidal functions for charts of data where you can find the amplitude by diving the difference by 2 and whatnot. Could anybody solve this for me and explain it preferably!