Answer:
is the correct answer.
Step-by-step explanation:
First of all, let us label the diagram as shown in the attached figure.
OR = 20'
QS = 16'
is the right angled triangle that we get.


From the given figure symmetry, we can clearly see that:
Side OP = OR - QS
OP = 20 - 16 = 4'
Now, let us use trigonometric identity of cosine in
.


Let the distance of ramp, OQ = x'
So, the above ratio becomes:

So, the correct answer is:
