please answer the question

Question

You drop a seashell into the ocean from a height of 40 feet above the water.

a. Write a function h​ that gives the height (in feet) of the seashell above the water after t​ seconds. 

b, How long does the seashell take to hit the water?

c, Find h(0.5)-h(1)

Answer 1

a) h = 40 - g t^2 / 2

b) solve for t when h=0

c) plugin t-values into a)