The height of water during the rise and fall of a tide is recorded.

when the water height h(in meters) at time t(in hours) starting when the level is equal to the mean level of 3 meters and has an amplitude of 2.5 meters and a period of 15 hours.

the formula is

Compute the rate of change of the water height and Find the highest and lowest values of h and the times at which they are taken.

how i can solve this ?? need help guys plz