I would have used graph b. Because it shows the decrease more than graph a.
16 ft
Explanation
Step 1
because the ligth comes in the same angle, we have 2 similar triangles .
so,as the triangles are similar,the ratio of the shorter leg to the bigger leg must be equal.

Step 2
solve for h

therefore, the heigth of the tree is 16 ft
0.4444444444444
is the answer for your question it repeats so your gonna want to put a bar notation.