A tree has height 1m when it was first planted. Assume that its height grows exponentially. (a) To measure the height of the tree, a person 20m away from the bottom of the tree will measure the angle of elevation to the top of the tree. After 2 years, the angle of elevation is 19. Find the height of the tree at that time. (b) Assuming that height grows exponentially, find the height of the tree after 5 years. (c) What is the angle of elevation to the top of the tree after 5 years? (assume the person is still standing 20m away from the bottom of the tree)